Meaning of Traffic Signals

Traffic signals are provided at road intersections. These are control devices that could alternatively direct the traffic to stop and proceed at intersections using red and green traffic light signals automatically.

The main requirements of traffic signals are to draw attention, provide meaning and time to respond and to have a minimum waste of time. we also see what are the types of traffic signals

Basic Requirements of Traffic Signals :

(1) Attention

The signals must attract the attention of its users. Factors affecting attention are :

• Position of placing the signals
• Height of placing the signals
• The size of lamp lens (usually 200 mm diameter is used)
• Design of signal face and head.
• Background of the lens (generally dark background is required for lighted lens).

(2) Meaning

Each indication of signal should convey one and only one meaning clearly without any misinterpretation.

Red : Vehicle must STOP
Green : Vehicle can GO
Red Yellow (Amber) : Be ready to GO.

(3) Response

Yellow (amber) interval provides time required for response Since it takes time to stop a moving vehicle, an immediate change from green to red does not give time for response.

(4) Respect

The signals which are installed at a location should be useful to road users and they must be respected (liked) by them.

Where Traffic Signals Should Be Installed ?

At each and every intersection it is not necessary to install a traffic signal Such a general installation of traffic signals in fact would cause traffic congestion. Traffic engineering data should justify this installation.

The following recommendations are followed :

(i) The average traffic volume for eight hours on both approaches should be at least 650 motor vehicles per hour on a major street with a single lane and 850 vehicles on the streets with two or more lanes.

(ii) Minimum pedestrian traffic of 150 or more per hour should cross the major street with over 600 vehicles per hour on both approaches (1000 vehicles per hour in the case of the main street with raised median).

(iii) If there is an interruption of continuous traffic flow on the major road which carries 1000 to 1200 vehicles per hour or when there is undue delay or hazard to the traffic of 100 to 150 vehicles per hour m one direction only during any eight hours on an average day.

So to complete the above recommendations we have to study various types of traffic signals which are available in all countries.

Types of Traffic Signals

Generally, a traffic signal is composed of three lenses, arranged vertically one above the other with a red lens on top, yellow or amber in the middle, and a green lens at the bottom.

The normal sequence of the traffic signal is red, .amber, green, amber, red, and so on. The following are the indications are given by the colors of signal.

Red: Vehicles must stop
Amber: Lights about to change
Green: Vehicles can proceed.

here i have list out and explain types of traffic signals

The traffic signals are classified into the following types :

1.Traffic control signals
A. Fixed time signals
B. Manually operated signals

C. Traffic actuated signals
(i) Fully actuated signal
(ii) Semi-actuated signal

2.Pedestrian signals

3.Special traffic signals

lets discuss one by one types of traffic signals

1. Traffic Control Signals

These types of traffic signals are provided at different locations like intersection, circles, crossways. they are provided with three colors red, yellow amber, and green in facing the direction of traffic. The purpose of this color is mention above at the starting of the article.

This types of signal are further classified in to follow categories.

A. Fixed Time Signals :

These types of traffic signals are set to repeat regularly a cycle of red, amber, and green lights. The timing of each phase of the cycle is predetermined based on traffic studies. These signals are the simplest type of automatic traffic signals which are electrically operated. These signals are also called Pre-timed signals.

These types of traffic signals cannot take into account the fluctuations in traffic flow and so they are satisfactory where fluctuation is small. Different cycle times may be used to take care of morning peak, evening peak, and non-peak hour traffic, by using different cycle lengths during those hours. The cycle length varies from 40 seconds to 120 seconds.

Advantages of Fixed Time Signals:

• Simple in construction
• Relatively inexpensive
• Most successfully used in linked systems requiring a fixed cycle length for a given pattern and speed of progression.

Disadvantages of Fixed Time Signals :

• Inflexible and hence may cause an avoidable delay.
• Require a careful setting.
• Sometimes the traffic flow on one road may be almost nil and traffic on the crossroad may be quite heavy. Yet as the signal operates with fixed timings, the traffic in the heavy stream will have to stop at. red phase.

B. Manually Operated Signals :

In these types of traffic signals, the traffic police control the traffic demand from a suitable point during the high peak hours at the intersection and vary the timings of these phases and cycle accordingly.

This method used when their is vary low traffic which is handle by traffic police officers.

Advantages of Manually Operated Signals

• Use when there is low traffic
• No first investment

Disadvantages of Manually Operated Signals

• This method is costly too much.
• Running cost is high.

C. Traffic Actuated Signals [Traffic Automatics Signals] :

These types of traffic signals are those in which the timings of the phase and cycle time are changed according to the traffic demand. The vehicles on any intersection approach are sensed by a detecting device (e.g. magnetic tape, loops, or pneumatic pads) placed in the road. By recording the vehicles as they cross the detector and by timing the interval between vehicles, the signals are automatically adjusted to give preference to the approach with the heaviest flow.

Types of Traffic Actuated Signals :

These types of traffic signals are classified into following two types

(i) Fully actuated signal
(ii) Semi-actuated signal

(i) Fully actuated signal

These have detectors located on each approach and assign the right of way to the various traffic movements on the basis of demand.

(ii) Semi-actuated signal

Where traffic on a heavy volume of high-speed arteries must be interrupted for relative light class traffic, semi-actuated traffic signals are often installed. For these signals, the detectors are placed only on the minor street.

Advantages of Traffic Actuated Signals :

• Usually reduces delay.
• Usually increases the capacity.
• It is adaptable to short-term fluctuation in traffic.
• It provides continuous operation under low volume conditions.
• It is most efficient for isolated intersections.

Disadvantages Traffic Actuated Signals :

• They are uneconomical. The cost is about two to three times the cost of a fixed time signals.
• Detectors are very costly to install and present very difficult maintenance problems.
• The actuated controller (a complete electronic mechanism) is much more complicated than fixed time controllers.

2. Pedestrian Signals

These types of traffic signals are basically used for the pedestrian. These types of signals are provided on various locations like schools, colleges, offices, and many more.

This type of signals allow pedestrian to cross the road.

The Indian standard on traffic signals prescribes the following symbols for pedestrians. The RED standing man represents the don’t cross indication and the GREEN walking man represents cross indication.

3. Special Traffic Signals

These types of traffic signals are used to warn the traffic flow.

When there is a red flashing signal, the drivers of vehicles must stop before entering the nearest cross walk at the intersection or at a stop line where marked.

Flashing of yellow signals are used to direct the drivers of the vehicular traffic to proceed with caution.

General Principles of Signal Design

The main objective of the design of signalized intersection should be to provide sufficient capacity for the volume of traffic approaching the intersection. The design should aim at minimizing total delay, building short queues, and providing a high probability of passing through the intersection on the first given period for most users. Signal timing should be in accordance with traffic flow on the intersection. The cycle lengths are normally 40 to 60 seconds for a two-phase signal. Longer cycle lengths may be adopted for complex traffic flow and for more than two phases

Indian practice is Red-Green-Amber. The amber interval is a transition interval between the termination of the green movement and the exhibition of a red indication. The amber period is generally 3 to 6 seconds, and red/amber is usually 2 seconds.

(1) In general practice time for red signal provide sum of green and amber signal.

(2) Towards the end of the red phase, for a short duration amber light is put on along, with the red light signal in order to indicate ‘get set’ to go. This phase is called ‘red amber’ or ‘initial amber’. The vehicles are not supposed to cross the stop line during the red amber period.

(3) Clearance time or clearance amber phase is provided just after the green phase before the red phase, to fulfil two requirements :

■ Stopping time for approaching vehicle to stop at stop line after signal changes from
green to amber.
■ Clearance time for the vehicle which is approaching the stop line at legal speed while
the signal changes from green to amber.

(4) Green time or go time is decided based on the approach volume per week to enable the
queued vehicles to clear off in most of the cycles.

Various methods for design of fixed time signals are:

1. Trial cycle method
2. Approximate method
3. Webster’s method
4. IRC method

Advantages of Traffic Signals :

1. Maintain orderly flow of traffic

2. Reduce certain types of accidents.

3. Improves safety and efficiency of movement of vehicles.

4. Pedestrians can cross the roads safely

5. Provides nearly continuous movement of traffic

6. More economical than manual control

7. Stop heavy traffic to allow slow moving traffic to cross the road safely.

8. Increase in speed along the major road traffic.

Disadvantages of Traffic Signals :

1. The rear end collision may increase.

2. Improper design and location of signals may lead to violations of the control system.

3. Failure of the signal due to electric power failure or any other defect may cause confusion to the road users.

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1) 10 Types of Parking And How To carry Out Parking Study In Traffic Engineering ?

2) TRAFFIC VOLUME STUDY: How To Carried Out 10 Traffic Volume Studies In Traffic Engineering

3) 6 Methods To Carried Out Spot Speed Study In Traffic Engineering  – Measurement of Spot Speed Study

The enormous increase in vehicles has created the need for parking spaces in metropolitan cities. In industrial, commercial, and residential places with multi-storeyed buildings, parking demand is particularly high. A parking study is performed to determine location, use, and adequacy of existing parking facilities. in this article, we will also see types of parking which are widely used in all countries.

The Object of Parking Study Is

■ To obtain information regarding demand for parking spaces.

■ For improvement and regulation of existing parking facilities.

■ For future development plans.

■ The demand for parking space

■ To decide about pay parking.

Some Definitions :

1. Parking Accumulation

The total number of vehicles parked in an area at a specified moment.

The curve of parking accumulation for a typical day is shown in fig. 2.20.

2. Parking Volume :

The number of vehicles parked in a particular area over a given period of time. It is usually measured in vehicles per day.

3. Parking Load :

The area under the parking accumulation curve during a specified period.

For example, In fig. 2.20, the hatched area represents the parking load in vehicle – hour for a period of hours from 6 AM. to 10 AM.

4. Parking Duration : 

The length of time spent by a vehicle in a parking space.

5. Parking Index :

Percentage of parking bays, actually occupied by parked vehicles as compared to the theoretical number of bays available.

Parking index =Number of bays occupied / Theoretical number of bays available

Types of Parking Study Surveys :

The type of parking survey to be conducted for formulating a comprehensive parking plan for an area can be very detailed in scope. The data collected and the degree of sophistication employed depends upon the funds available.

The Various Parking Surveys Usually Conducted Are :

(i) Parking space inventory

(ii) Parking usage survey by patrol

(iii) Questionnaire type parking usage survey

(iv) Cordon count

(i) Parking Space Inventory :

The very first step in a parking survey is to collect the data regarding the amount, type, and location of space actually available for parking in an area. The area to be surveyed should first be delineated. The central business area is usually the area where parking is needed. The area surrounding the central business place where the parking spills over should also be included in the survey. 

The survey area is then subdivided on a street – by – street basis and subdivisions marked on a map. Sketch plans of the streets are’ then prepared. The data on parking facilities should be recorded on the sketch plans using suitable symbols. 

The items to be recorded on sketch plans are :

■ The total length of kerb

■ Number of parking spaces provided in the street

■ Street width

■Location of bus stops, bus bays, pedestrian crossing, fire hydrants, etc.

■Traffic measures like prohibited turns, one-way traffic, the exclusive bus lane, etc.

■ Private streets

■ Vacant or unused land suitable for new parking.

A typical sketch plan for a street with the above information recorded is shown in fig.

Off-street parking facilities should be recorded separately, indicating the type, capacity, parking pattern, parking charges, entrances, and exits.

(ii) Parking Usage Survey By Patrol :

The purpose of parking usage survey is to obtain data on the extent of usage of parking spaces. The survey will include counts of parked vehicles at regular intervals through a period, covering both the morning and evening peak period, and the parking accumulation and turn-over. The survey can be for on-street or off-street parking. 

The method consists of making periodic observations of parked vehicles on each patrol. For off-street observations, the entire parking space can be patrolled or the entrances and exits may be observed simultaneously.

Mapping The Street System :

The first step is to prepare a map of the street system that will be covered by the patrol, showing therein subdivision into sections. Street junctions make convenient points for determining the sections.

The recording can be for both sides of the road or separately for each side. The map and forms should clearly show the direction of travel by the patrolman and the sides where observations are to be recorded.

Frequency of Patrol :

Though more frequent patrol result in more accurate data, the fieldwork and subsequent analysis becomes more tedious.

Method of Observation :

Normally patrols are on foot, but where vehicles are not parked to close to one another, a  moving car may also be used. As an aid, a tape recorder may be used to record the registration numbers of vehicles.

Timing of Survey :

The survey could be done on a typical week or day, free from factors likely to result in non representative data. The period of the survey is usually 10 to 12 hours, so as to cover the arrival and departure of commuters and shoppers.

(iii) Questionnaire Type Parking Usage Survey :

This type of parking survey involves interviews with the drivers who use the parking facilities. As a result it is possible to collect the information on the extent to which the existing facilities are being used, the journey purposes of car parkers, the parking demand at different prices, etc.

The information collected should include :

■ Address of origin of the trip

■ Trip purpose

■ Time of departure from the parking place

■ Type of parking space, etc.

■ Address of destination of the trip

■Time of arrival at the parking place

■Type of vehicle 

TYPES OF PARKING :

There are basically two main types of parking. 

1) On-Street Parking 

2) Off-Street Parking 

 Let’s discuss all types of parking one by one.

1) ON-STREET PARKING

In this type, the vehicles are parked near the edge of curb of the road. Thus, it is also called Kerb parking.

Methods of On-Street Parking :

(i) Parallel parking 

(ii) 30° angle parking

(iii) 45° angle parking 

(iv) 60° angle parking

(v) Right angle parking

(i) Parallel Parking 

Parallel parking consumes the maximum curb length which decreases with an increase in the angle of parking. The minimum kerb length is consumed by right-angle parking, which accommodates nearly 2 times the number of vehicles as parallel parking.

But, the parallel parking makes the least use of the width of the street, and this is an important consideration in narrow streets. In the case of right-angle parking, the maximum road width is utilized.

From the viewpoint of maneuverability angle, parking seems to be better than parallel parking which usually involves a backing motion. Delay to traffic is minimum with angle parking.

Thus, it is recommended that in general parallel parking should be preferred on the streets. On exceptionally wide (wider than 20 m) and low volume streets, parallel parking may be provided.

That’s why parallel parking is best parking in all types of parking in on street parking.

(ii) 30° Angle Parking

In these types of parking one side of the vehicles are place at the angle of 30 degrees with respect to curb.

(iii) 45° Angle Parking 

In these types of parking one side of vehicles are place at the angle of 45 degrees with respect to curb.

(iv) 60° Angle Parking

In these types of parking one side of vehicles are place at the angle of 60 degrees with respect to curb.

(v) Right Angle Parking

In these types of parking one side of vehicles are place at the angle of 90 degrees with respect to curb.

Parking Prohibition

It is desirable to prohibit parking at certain locations and for a period to ensure safety and convenience.

(i)      Near intersections

(ii)     Narrow streets

(iii)    Pedestrian crossings

(iv)    Near structures like a bridge, tunnels, etc.

(v)     In front of entrance driveways leading to houses and buildings.

OFF-STREET PARKING:

In this type of parking, a special area is prepared so that its reduce traffic on on-street parking.

Need For Off-Street Parking :

In case of on-street parking, vehicles are parked near the edge or curb of the road which may create many problems like congestion, accidents, etc. To overcome these difficulties, off-street parking are designed. The main purpose of off-street parking is to prevent congestion of the public right of way and to promote the safety and general welfare of the people.

Types of Off Street Parking :

(i) Surface car parks 

(ii) Multi-storey parks

(iii) Roof parks 

(iv) Mechanical car parks

(v) Underground car parks

Since these facilities are costly to provide and maintain, a comprehensive study should be done before planning such facilities.

(i) Surface Car Parking:

Surface car parks, properly located and developed on a piece of vacant land or surrounding an office complex or supermarket, are very popular with the motorists. A stall size of 2.5 m x 5.0 m is probably adequate for Indian conditions.

If the surface car park is to be operated with a fee-charging system, there should be arrangement for collecting the fees.

In this type of parking generally area required more then other parking so its used when widely area is available.

(ii) Multi-Storey Car Parking :

Surface car parking consume too much of the precious land in the heart of the city and are not, therefore, always feasible. In such cases multi-story car parks are an alternative choice.

Multi-story car parking has become common and popular in megacities like Mumbai, Delhi, Chennai, Bangalore, etc.

Multi-story car parks are designed for a capacity of about 400 to 500 cars. About five floors of parking is the upper limit as a large number of floors tends to increase the time for unparking the car.

In this type of parking generally area required is less compare to surface car parking because we have advantages of third dimension ( Hight ).

Some of the desirable standards for designing of the multi-story car parks are :

■ The gradient of a ramp: 1 in 10

■ Clear height between floors: 2.1 m 

■ Parking stall dimensions: 2.5 m x 5.0 m

■ Inside radius of curves: 7 m

■ Width of traffic lane: 3.75 m

■ The gradient of sloping floors: not steeper than 1 in 20.

■ Loading standards : 400 kg/Sq.m (4 kN/sq.m)

(iii) Roof Parking :

Parking of vehicles on rooftops is a very popular method of solving the parking problems in many cities. Access ramps or mechanical lifts provide the necessary access to the roofs. The rooftop is specially designed to carry the road of parked vehicles.

This type of parking are not commonly used in all country but they are adopted in U.K.  

(iv) Mechanical Car Parking :

Mechanical car parks provide for the lifting of cars from floor to floor by means of a lift and transfer of cars to and from the parking stall by means of mechanically operated transfer dollies or cradles.

Since the ramps and aisles are eliminated in this system, it is more economical in space as compared to the ramped system multi-story parking. The main disadvantage of this system is the higher cost of maintenance and the possibility of breakdown due to mechanical or power failure.

This type of parking is widely used in indrustrial areas because they are easily available and they are movable.

(v) Underground Car Parking :

The main advantage of underground car park is the least intrusion they cause to the aesthetics of a place. An excellent example is the underground parking below Hyde park in

London and in Connaught Place in New Delhi.

These types of parking can be built in the basement of any multi storeyed building or below an open space. Since the work involves large quantities of excavation, construction of retaining walls, ventilation and lighting, such car parks tend to be very costly.

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]]> https://engineeringbrother.com/10-types-of-parking-traffic-engineering.html/feed 0 531 https://engineeringbrother.com/traffic-volume-study.html https://engineeringbrother.com/traffic-volume-study.html#respond Wed, 16 Sep 2020 10:55:00 +0000 Continue Reading....TRAFFIC VOLUME STUDY: How To Carried Out 10 Traffic Volume Studies In Traffic Engineering

TRAFFIC VOLUME STUDY

Traffic volume (flow) is variable.  It is of great importance to the traffic engineer.  It is essentially the quantity of movement per unit of time at a specified location.  The quantity of movement may be either of single traffic unit-pedestrians,  cars,  buses or goods vehicles,  etc. The time period will depend on the purpose of the study. in this article, we will study how to carry out a traffic volume study?

Traffic Volume 

The number vehicles crossing a section of road per unit time at any selected period is called traffic volume And study of traffic volume is known as a traffic volume study.

The unit of traffic volume is vehicles per hour or vehicles per day.

 Objects and uses of traffic volume study :

1. Traffic volume study is accepted as a true measure of the relative importance of roads and in deciding the priority to improvement and expansions.

2.  Traffic volume study is used in planning, traffic operation and control of existing facilities.

3.  Used in planning and designing the new facilities.

4.  For the analysis of traffic patterns and trends.

5. Classified  volume  study is useful in ‘structural design of pavements, in geometric design and in computing roadway capacity.

6. For planning sidewalks, crosswalks, subways, etc.

7.Turning movement study used in the design of intersections in planning signal timings, etc.

8. To know the various types of the vehicle using the road.

 The following studies are carried out in the traffic volume study 

1. Classification of traffic, i.e. buses, trucks, cars, auto-rickshaws, cycles, bullock carts, pedestrians, etc.

2. Number of vehicles in each class.

3. The direction of each class of traffic flow is also noted.

4. At intersections, the traffic flow in each direction of flow including turning movements is recorded.

5. The peak traffic period is also noted.

TYPES OF VOLUME COUNTS

Hourly traffic volumes and average daily volumes are those commonly used in the planning, design, and operation of highway facilities. Traffic demands in the vehicle per hour per lane are of great significance in dealing with practical traffic problems.

1. Peak Hour Volume (PHV) or Peak Hour Flow (PHF):

The highest hourly volume in a day is called peak hour volume. It is the maximum number of vehicles that pass a point on a highway during one hour.

There is one peak in the morning and another in the evening referred as ‘morning peak hour’ and ‘evening peak hour’.

It is used for,

1. Functional classification of highways (dike arterial, sub-arterial, collector, and local streets for urban roads).

2. The geometric design  of  highway  (like  the number  of  lanes,  intersection  signalization, channelization, etc.)

3. capacity analysis

4. Parking demands and regulations.

5. Planning and location of traffic control devices, (traffic signs, signals, markings)

6. Location of interchanges.

2. Average Annual Daily Traffic (AADT) :

It is the average of 24 hours volume count collected every day in the year.

It is useful for;

1.Planning major streets

2.Improvement, construction, or reconstruction of roads

3.Estimating highway user revenue

3. Average Daily Traffic (ADT) :

The total volume during a certain number of days, divided by that number of days is called average daily traffic.

Fig.  Shows the typical traffic pattern throughout the day, week, and the year.

4. Classified volumes :

These are used for,

1.Geometric design with respect to minimum turning paths, clearance, grade

2.Structural design of pavements, bridges.

3.Estimating highway user revenues.

4. Short counts less than an hour :

5. Short counts less than an hour :

These are used for,

1. Analyzing maximum rates of flow and, variation within the peak hour

2. Providing economical means of obtaining volume data.

3. Determining capacity limitations in urban areas.

6. Cordon count volumes :

These are made for,

1.Planning parking facilities

2.To obtain accumulation of vehicles inside the cordon area.

7. Pedestrian volumes :

These are utilized in planning the crosswalks and signals for pedestrians.

8. Turning movements counts :

These are used in

1.Design of intersection and interchanges

2. Planning of signal timings

3. Planning turn prohibitions

4.Channelization, etc.

METHODS OF TRAFFIC VOLUME STUDY 

COUNTING OF TRAFFIC VOLUME STUDY :

The traffic volume study counts may be done by mechanical counters or manually.

 

(A)   Mechanical Counters (Automatic Counters) :

These may be either fixed (Permanent) type or portable type. The mechanical counter can automatically record the total number of vehicles crossing a section of the road in the desired period. The working maybe by the effect of impulses or stimuli caused by traffic movements on a pneumatic hose placed across the roadway.

Advantages :

1.It can works throughout the day and night for the desired period, recording the total hourly volume.

2. It does not require any supervision

3.It is suitable for long counts.

Disadvantages

1.It is not possible to get the traffic volume of various classes of traffic.

2.It does not give the details of turning movements.

3.The impulses caused by light vehicles may not be enough in some cases to acute the counter.

4.It is not possible to record the pedestrian traffic.

Types of Automatic Counters :

Various types of automatic counters are :

1.Pneumatic tube (road tube)

2.Electric contact device

3.Co-axial cable

4.Photo-electric  device

5.Radar

6.Infra-red device

7.Magnetic device

8.Ultrasonic device

(1)    Pneumatic tube (Road tube) :

A thick walled flexible tube (10-12 mm diameter, 3 mm thick) with one end sealed is clamped  to  the road surface at right angles to  the pavement.  The other end  of the tube is connected to a diaphragm or counter. At the sealed end a small air release hole is provided to avoid bounced impulses. As a vehicle wheel crosses the tube it compresses it, causing an air ‘shock wave’ to travel along the tube, operating a simple ‘make and break’ circuit of the counter as shown below.

 

(2)    Electric contact device :

A pair of steel strips are contained in a rubber pad which is burried beneath the road surface. On being pressed by the weight of a moving axle the steel strips come into contact with each other and cause the electric current to flow. Electric contacts are installed in each lane.

(3)    Co-axial cable :

A coaxial cable is clamped across the road surface with the capability of generating signals with the passage of axles. These signals actuate a transistorized counter. The advantages associated with this type of detectors are their better reliability and performance on inferior type of surfaces and their lesser susceptibility to damage.

(4)    Photo-electric device :

On one end of the road is a source of light which emits a beam across the road. At the other end is a photocell which can distinguish between the light beam and absence of the light beam.  The passage of vehicle in  the path  of the light beam obstructs the beam and  causes detection by the photo cell.

The difficulty is that obstruction can be caused by pedestrians and that more than one vehicle in the different traffic lanes, will register only one vehicle.

(5)    Radar :

Doppler effect is a well-known phenomenon in physics which enables the detection of vehicles moving at a speed. When a moving object approaches or recedes from the source of signals, the frequency of the signal received back from the moving the object will be different from the frequency  of the signal emitted by the source.  This difference in  the two  frequencies causes the detection of a moving vehicle. The initial cost of this device is no doubt high, but its accuracy and reliability are good. It is also not damaged by traffic.

(6)    Infra-red device :

This device utilities a pick-up cell, which is similar to a photoelectric cell, but is sensitive to  infrared  (heat) radiation,  rather than  to  visible light.  The unit is mounted  above the road surface on a bridge or sign structure etc.

(7)    Magnetic device :

In this, detection is done by a signal or impulse caused by a moving vehicle and disturbing a magnetic field. The unit is installed in each lane immediately below the road surface. It is more durable but more expensive than a pneumatic detector.

(8)    Ultrasonic device :

This is similar in its operation to a radar unit. A beam crosses the road and is broken by the passage of a vehicle.

(B)   Manual Counts :

In  this  method,  the  members  of  field  team  collect  the  necessary  information  on  the prescribed record sheets at the selected points of roadway.

 Advantages :

1. It gives a classified volume of each  category  of traffic,  namely,  buses,  cars,  trucks, auto-rickshaws,  cycles,  scooters,  pedestrians,  etc.  which can not be collected by mechanical counters.

2.  The direction of each class of traffic at intersection is also be recorded.

3.  The number of occupants in vehicles are also recorded in this method. 

Disadvantages : 

1. It is not possible to have manual counts for all the 24 hours of the day and on all days round the year.

2. It is tedious, laborious and costly.

 

 

MOVING OBSERVER METHOD [FLOATING CAR METHOD] 

 

This method is also known as Wardrop Charlesworth method. It was developed in England. This method consists in counting the number of cars met, number of cars overtaken, and the time taken to travel by the observer, once moving against the traffic and once moving along with the traffic.

 

The floating car method is generally followed in India. Here we have a test car with four observers in it which is floating, i.e. which is travelling at approximately the same speed as that of the traffic.

 

The first observer equipped with two stopwatches is an observer to record delays. At strategic locations such as bridges, intersections, roads in the vicinity of markets etc. he observes with the help of two stopwatches the time required to negotiate these focal points, i.e. he observes the delay time.

The second observer in the car notes the cause of this delay either in the tabular form or with vivid descriptions.The third observer record the number of vehicles overtaken by the floating car or the number of vehicles that overtakes the floating car, in specified time.

The fourth observer notes the number of vehicles traveling in opposite direction in each trip.

Advantages of the method :

(i) The moving observer method gives an unbiased estimate of the flow.

(ii) As compared to the stationary observer method, the moving observer method is equivalent to a stationary count over twice the single journey time. Hence it is economical in manpower.

 

(iii) It gives mean values of flow and speed over a section, rather than at a point. Thus it gives directly the space mean speed, whereas spot speed studies give the time-mean speed.

(iv) It gives additional information on stops at intersections, delays, parked vehicles, etc.

(v) It enables data on speed and flow to be collected at the same time.

VIDEOGRAPHY METHOD FOR TRAFFIC VOLUME STUDY:

 

The videography is carried out for the stretch of road about 20 to 30 m. The entry and exit of the vehicle on the selected approach should be covered in the videography. The start time of the video is set to zero. The movement of the vehicles are recorded for an hour. After the end of the videography, the vehicles are counted on the screen of the computer or DVD. The entry time of the vehicle and exit time of the vehicle is recorded for the vehicles on the selected stretch.

The distance passed by the vehicle per unit time is worked out.Video photography gives a permanent record of volume counts. Its analysis can be done conveniently in the office by replaying the cassette on a TV monitor.

PASSENGER CAR UNITS (PCU) FOR TRAFFIC VOLUME STUDY:

 

Different classes of vehicles such as cars, buses, trucks, autorickshaws, scooters, cycles, bullock carts, etc. are found to use the common, roadway facilities without segregation on most of the roads. Such a traffic flow is called heterogeneous traffic flow or mixed traffic flow.

The different vehicle classes have a wide range of static characteristics such as length, width, etc. and dynamic characteristics such as speed, acceleration, etc. It is rather difficult to estimate the traffic volume and traffic capacity of roadways under mixed traffic flow.

It is a common practice to consider the passenger car as the standard vehicle unit to convert the other vehicle classes and this unit is called Passenger Car Unit (PCU).

PCU =Capacity of roadway with passenger cars only/Capacity of the roadway with that class of vehicle

PCU indicates the space required for a vehicle on a road. For example,

PCU for the car is 1 and that for the bus is 3, it means the space required for a bus on the road is three times more than that required for a car.

PCU values for different classes of vehicles as per IRC : 64-1990 are given in the table .

 Factors affecting PCU :

The various factors affecting PCU of vehicle class related with vehicle, traffic stream,

roadway and control conditions are listed below :

(a) Vehicle Characteristics :

■ dimensions (length, width etc.)

■ power

■ speed

■ acceleration and braking characteristics

(b) Traffic stream characteristics :

■ Gap (transverse and longitudinal) between moving vehicles.

■ Composition of different vehicle classes

■ Mean speed and speed distribution.

■ Ratio of volume to capacity of the road.

(c) Roadway characteristics :

■ Road geometries (including gradient and curves)

■ access control

■ rural/urban

■ intersections (number and type)

(d) Control of traffic :

■ Speed limit

■ One-way street operation

■ Traffic control devices (signs, markings, signals etc.)

From the above factors, it is seen that PCU value of a particular vehicle class cannot remain a constant value. It is a dynamic value changing with roadway, traffic and control conditions. Out of the above factors, the most significant factors are size (Length and width) of vehicle, average speeds of traffic stream and gap (transverse and longitudinal) between the vehicles.

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1. 6 Methods To Carried Out Spot Speed Study In Traffic Engineering
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Spot Speed

This is the instantaneous speed of a vehicle at a specified section or location.

Important Definitions For A Spot Speed Study 

A)Average Speed:

Average speed is the average of the spot speeds of all the vehicles passing a given point on the roadway.

B)Running Speed:

 It is the average speed maintained by a vehicle over a particular stretch of road, while the vehicle is in motion.

Running speed = distance traveled by a vehicle/time taken (excluding delay)

C)Travel Speed (Overall Speed) :

 It is the effective speed with which a vehicle traverses a particular route between two stations. It is also called Journey speed

=Total distance traveled/Total time taken (including delays)

 Location And Time Of Spot Speed Study :

 A)Location :

1. At all major highways.

2. At all high accident frequency points

3. At all points where installation of traffic signals and stop signs are contemplated.

4. At other representative locations for collecting basic data for future planning.

B)Time of Study :

1. One hour between 9 to 12 a.m.

2. One hour between 3 to 6 p.m.

3. One hour between 5 to 10 p.m.

 The spot speed studies are usually made in good and normal weather.

Measurement of Spot Speed Study

 The study is useful in any of the following aspects of traffic engineering :

1. To use in planning traffic control and in traffic regulation.

2. For highway geometric design

3. To use in accident study

4. To study the traffic capacity

5. To decide the speed trends.

Measurement of Spot Speed Is Divided Into Three Parts

BY MEASURING THE TIME REQUIRED TO TRAVEL KNOWN DISTANCE

This also divided into the following parts

A)Long Base Methods

1) Direct Timing Procedure

2) Enoscope Pressure

3) Contact Tubes

B)Short Base Methods

1)Electronic Meter Method

2)Radar Speed Meter

3)Photographie Method

Selection of Base Length:

For long-base methods, the Institute of Traffic Engineers (1965) has recommended certain base lengths for spot speed determination at different average speed ranges of the traffic stream.

Long Base Methods

A) Direct-Timing Methods:

This is the best and most direct method for spot speed determination. Two observers are stationed at a convenient distance (50 m) specified they will see one another. the first one starts a stop-watch as a vehicle crosses the first indicator and stops it on a signal from his counterpart the instant the vehicle touches the opposite end of the section.

If the timing is finished by one observer, the measurement may be made up of a convenient point within the section on one side of the road at a rather higher elevation so both the timing spots will be seen directly.

From the known distance and therefore the measured time intervals, speeds is calculated. a talented observer can read a stop-watch to an accuracy of 0.2 second. If the observer can station themselves in an not easily seen way, the speeds calculated aren’t influenced by the driver’s reaction to figure. The disadvantages of this approach are that the readings are influenced by the observer’s interval and also the parallax effect in observing the vehicle position.

B) Enoscope :

Enoscope is a mirror box supported on a tripod stand. In its simplest principle, the observer is stationed on one side of the road and starts a stopwatch when a vehicle crosses that section.

An Enoscope has placed at a convenient distance of say 50 m in such a way that the image of the vehicle is seen by the observer when the vehicle crosses the section where the enoscope is fixed and at this instant, the stopwatch is stopped.

The time required for the vehicle to cross the known length is found and is converted to the speed in kmph.

 The main advantage of this method is that it is simple and cheap equipment and is easy to use.

The main disadvantage of this method is that the progress is too slow to  spot out typical vehicles and the number of samples observed will be less.

 The possibility of human error is high.

Spot Speed Study By Two Enoscopes

In this method, the observer stands between two enoscopes. When the image of the vehicle is seen in the enoscope at A, stopwatch is started and the instant, when the image of the vehicle is seen at B, the stopwatch is stopped.

C) Pressure Contact Tubes :

 In this method, pneumatic tubes are used as detectors to indicate the time of entering and leaving the base length.

When a vehicle passes over the tube laid at the first reference point, an air impulse is sent, which activates an electromagnetically controlled stopwatch in the hands of the observer.

When the vehicle passes over the second tube, the stopwatch automatically stops. The reading is noted by the observer. Alternatively, the readings can be recorded by automatic data recorders.

The main disadvantage of this method is that the contact tubes are easily seen by the drivers and this may affect their behavior.

Short-Base Methods:

Here, the base length is very short, say 2 m to 3 m, and electronic instruments are used along with pneumatic table detectors. Recording may be manual or automatic.

A) Electronic Meter Method

In this method requires the use of pneumatic tube and air switch, or electric contact stripes as detectors. On actuation, the current in milliamperes is allowed to accumulate in a condenser for a period time of two electric pulses from the switches on the road. Vehicle speeds is recorded only manually but the meter is calibrated to read the speed in kilometer per hour (km/h)

B) Radar Speed Meter

Radar speed meters work on the principle of the ‘Doppler effect’.

According to this principle, the speed of a moving body is proportional to the change in the frequency between the radio wave transmitted to the moving body and the radio wave received back.

The instrument directly measures the speed, and an accuracy of at least t 1.5 km.ph. is possible.

The instrument is battery operated and is portable. The speed meter is so kept that the angle between the direction of travel of the vehicle and the axis of transmission of the radio waves is as low as possible, say within 20°.

The instrument is set up near the edge of the carriageway at a height of about 1 m. The speeds of vehicles in both directions can be observed by this method.

C) Photographic Methods

Photography with time-lapse cameras has been successfully used to determine spot speeds of vehicles even in crowded zones. Photographs are taken at fixed intervals of time (say, one second per exposure) using a special camera. 

The passage of any vehicle can be traced with reference to time by projecting the exposed film on a screen. Video cameras also may be used for the purpose.

PRESENTATION OF SPOT SPEED DATA

To facilitate easy computations, the first step in the analysis of spot speed data is to group them into speed-class intervals and a frequency distribution table are constructed, as given below.

Table 2.2 Frequency distribution of spot speed

The Spot Speed Study Data Can Be Presented Graphically In The Following Ways :

1. Histogram and frequency distribution curve

 2. Cumulative frequency curve

 1. Histogram And Frequency Distribution Curve:

 The histogram is a plot between speed interval (speed range) and frequency %. A frequency distribution curve, of spot speeds is plotted with average values of each speed group of vehicles on the x-axis and % of the vehicle (frequency %) on the y-axis.

Thus, the frequency distribution curve is found by rounding off the histogram so that the area of the frequency curve is equal to the area of the histogram.

Modal speed: The speed corresponding to the peak of the frequency distribution curve is called modal speed.

 The modal speed indicate the speed at which the greatest proportion of vehicles travel.

2. Cumulative Frequency Curve :

The cumulative frequency curve is plotted between cumulative frequency percentage and upper limit of speed in each speed group.

It is used for determining the number of vehicles travel above or below given speed.

85th percentile speed:

The speed corresponding to 85% cumulative frequency in the cumulative speed distribution the graph is known as 85th percentile speed.

 85th percentile speed is the speed at or below which 85% of the vehicles are passing the point on the highway or only 15% of the vehicles exceed the speed at that spot.

85″ percentile speed is also known as safe speed limit.

98th percentile speed is taken as the design speed for a highway.

The 15th percentile speed is the minimum speed. 

Time Mean Speed And Space Mean Speed :

1. Time – mean speed (Vt)

The average speed of different vehicles measured at a particular section of the road is called time mean speed.

where,

V = time mean speed

Vi =instantaneous speed of the ith vehicle

 n = No. of the vehicle observed

 2. Space mean speed (Vs):

It is the speed of vehicles on a road length measured at different sections but at the same time.

Measure of Central Tendency And Dispersion

1. Arithmetic Mean (x):

One of the measure for determining central the tendency of speed data is the arithmetic mean, which is the average of the observed speed.

where,

Exi= arithmetic mean speed

fi = number of speed observations in a group I

xi= midpoint speed of group i

2. Standard Deviation (s):

The standard deviation of a grouped frequency distribution is given by:

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1. Deterioration of Concrete Its Causes and Prevention
2. Water Demand , Its 5 Types  And 11 Factor Affecting Water Demand of City 
3. 14 Types of Cement And Their Practical Uses in Concrete Construction

Hello, guys, we are back with another article, This article is about new innovations in road transportation. Basically, we used reinforcement concrete roads and bituminous roads but nowadays there is the trend of making solar roadways.

Solar roadways are basically used to generate electricity and reduce global warming. The first implementation of this roadway is in France.

WHAT ARE THE SOLAR ROADWAYS ?

Basically, the solar roadways are the road surface which generates Electricity by using a solar photovoltaic cell. These cells are embedded below the tough glass layer.

solar roadways

NOW QUESTION ARRIVE THAT WHAT IS PHOTOVOLTAIC CELL ?

A photovoltaic cell is a cell made by joining N-TYPE and P-TYPE silicon cells.
N-TYPE silicons are that in which silicon is doped with phosphorus and in P-TYPE silicon is doped with boron.

solar photovoltaic cell for solar roadways

When these two doped silicons join with each other then it will make a junction at end of P-type and N-type silicon. This will make a permanent electric field at the joint. And when sun energy applied in form of light or heat at the junction then it will increase potential and there will be a flow of electric current this is the operation of a solar photovoltaic cell.

CONSTRUCTION COMPONENTS OF SOLAR ROADWAYS

We have classified the construction component of the solar roadways into three-part.

1)Glass layer
2) Electronic layer
3)Base Platelayer

Lets we discuss these components of solar roadways step by step.

1) Glass Layer For Solar Roadways

Glass layer for solar roadways

This is the top layer of the road. The glass is durable, fire-resisting, and sufficiency tough to carry vehicle loads.

2) Electronic layer For Solar Roadways

Electronic layer for solar roadways

This layer is provided below the glass layer. This layer consists of a solar photovoltaic cell And it transfers light energy to electric energy. It also contains a microprocessor board with support circuitry for controlling heating elements in view of reducing snow.

3)Base Plate layer For Solar Roadways

Base plate layer for solar roadways

This layer provides at bottom of the Electronic layer. This layer collects all electric energy and transmits & distributes energy to commercial use or industrial use.

CONSTRUCTION OF SOLAR ROADWAYS

construction of solar roadways

Construction of the solar roadways is difficult to compare to the normal roadway. In construction, the first base plate layer is provided with suitable wiring. Above this layer Electronic layer is provided which is generally a solar photovoltaic cell and wiring is provided to connect both layers to each other. Above these layers, a glass layer is provided which protects these layers and used for transportation.

WORKING OF SOLAR ROADWAYS

Working of solar roadways

The working of solar roadways is simple in which light of the sun falls on the road surface which is converted to electric energy by means of photovoltaic cell and distribute by base player layer.

CAN CAR’S MOVE ON SOLAR ROADWAYS ??

When we think about these solar roadways a question arises that can cars move on this roadway? If vehicles cant move then this road is useless.

The answer to the question is ‘Yes We Can’

We can drive a two-wheeler, four-wheeler, and light loaded vehicles. But it’s difficult to drive heavily loaded vehicles. So this type of roadways is used in city where heavy loaded Vehicles are not permitted.

WHY WE USE SOLAR ROADWAYS ?

There are two main reasons behind using this types of roads.

1) Global warming
2)To generate electricity

1) Global warming

Global Warming

As we know the problem of global warming is increasing day by day. So to reduce global warming we have to use fewer amount coals,  petroleum products for doing this we have to go with an electrical motor. Ultimately solar roadways will be used to supply electricity to electric motors.

Anti global warming measures

2)To generate electricity

Solar roadways are used to generate electricity which is used as a commercial or industrial.

FEATURES OF SOLAR ROADWAYS

The various type of features are

1) Illuminate Road

 Lanes of roadway contain LED light which are directly operated by electronic layer. This LED illuminates the road surface.

2)Electric Vehicles

The energy which is generated by the road surface is used for filling electricity in an electric car.

3)Snow/Ice management

The road heats themselves with their embedded heating element so its reduces snow or ice on top of the road surface.

4) Improve power lighting

ADVANTAGE OF SOLAR ROADWAYS

The various advantages of solar roadway are

1.Electricity generation
2.Eco-friendly
3.The solar road plate is completely recycled or reusable
4.Ice/snow management as shows above.
5.Reduction in the usage of nonrenewable energy.

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