traffic engineering

TRAFFIC

ENGINEERING

Source: ETH (Institute for Transport Planning and Systems), Zurich

Possible Areas of Research in TE• Develop models to better replicate real traffic conditions• Improve understanding of traffic phenomena• Contribute to a better definition of the role of cars in cities, while assessing

their external costs and impacts• Understand and quantify how different technologies and management

strategies influence the performance of transportation systems• Develop innovative solutions to improve traffic performance and reduce

congestion both in highways and urban networks• Identify new and efficient methods for using in-vehicle and infrastructure

technologies to improve traffic conditions• Optimize the operations of transportation systems from a multi-modal

perspective

TRAFFIC ENGINEERING

• Traffic Characteristics• Traffic Studies and Analysis• Traffic Operations • Planning and Analysis• Geometric Design• Administration and Management

TRAFFIC CHARACTERISTICSTraffic Characteristics

Road User

Physical

Mental

Psychological

Environmental

Vehicular

Vehicle Dimensions

Weight of Loaded Vehicle

Power of Vehicle

Speed of Vehicle

Braking Characteristics

It consists of 1. Human Element2. Vehicular Element

ROAD USER CHARACTERISTICS

• PHYSICAL: Vision, Hearing, Reaction to different traffic situations, Strength

• MENTAL: Knowledge (of Vehicle characteristics), Skill, Intelligence, Experience,

Literacy (w.r.t. Traffic Rules as well as general Literacy)

• PSYCHOLOGICAL: Affect the reactions to the reaction to traffic situations

Reactions to distractions, drivers’ mental status, Emotions

(Attentiveness, anger, fear, impatience, general attitude

towards Traffic Rules & Regulations) and Maturity of Drivers

• ENVIRONMENTAL: Traffic stream Characteristics, Lack of Facilities (like design

of overtaking zones, uneven surface, etc.),

Motivation/Reason for coming/going (in a hurry, casual, etc.)

TRAFFIC CHARACTERISTICS

VEHICULAR CHARACTERISTICS: The criterion for Road Design is to cater for the needs of existing and anticipated (forecasted) traffic. So, the Vehicular Standards should preferably be similar throughout a country (big region), so as to provide ease of Planning and Design of Highway Networks.


Vehicular Characteristics

STATIC

Vehicle Dimensions

Weight of Loaded Vehicle

DYNAMIC

Power of Vehicle

Speed of Vehicle

Braking Characteristics

VEHICULAR CHARACTERISTICS: STATIC


Dimensions

LengthDesign of Horizontal Allignment,

Minimum Turning Radius, Width of extra pavement, Vertical Curves,

OSD, Capacity and Parking Studies

Max Length: 11 m to 18 m

HeightHeight of

Overbridges, underways,

electric lines, etc

Max Height: 3.8 m (single deck), 4.75

(Double deck)

WidthWidth of lanes,

shoulders, parking facilities, Capacity

of Roads

Max Width: 2.50 m

VEHICULAR CHARACTERISTICS: STATIC

• WEIGHT OF LOADED VEHICLE: • Affects pavement thickness and gradient. (though Limiting Gradients are governed by weight and power of the vehicle)Max Gross Weight: 12 tonnes (both axle single tyre trucks)

52.2 tonnes (tractor trailer type 3-3)(6+18+10.2+18= 52.2 tonnes)


TRUCK/TRACTOR TRAILER

Max Weight on Front Axle (FAW)

6 – 9 tonnes 10.2 tonnes (Type 2-2 and above)

Max Weight on Rear Axle (RAW)

6 – 18 tonnes 10.2 – 18 tonnes

VEHICULAR CHARACTERISTICS: DYNAMIC

• POWER OF VEHICLES:

Total Hauling Capacity and Power required to overcome total tractive resistance are used for the determination of Speed and Acceleration

This is useful for Traffic Regulation, Planning and Design

*Total resistance to traction consists of Inertia, Rolling Resistance, Air Resistance and Grade Resistance.



• SPEED OF VEHICLE:

It affects the design of

a. Sight Distances

b. Superelevation, Length of Transition Curves and Limiting Radius on Horizontal Curves

c. Length of Transition Curves on Vertical Curves

d. Width of pavements and shoulders

e. Design Gradient

f. Capacity of Traffic Lane

g. Design and Control Measures on Intersections



• BRAKING CHARACTERISTICS:

Depend on design and type of braking system (Mechanical, Fluid or Air Brake) and its efficiency.

Affects the safety of vehicle operations, stopping distances, spacing between two consecutive vehicles.

Thus, Highway Capacity and Overtaking Sight Distances are also indirectly affected.




Braking Test

Measurement of Skid Resistance under prevailing conditions (type of pavement and the desired speed of vehicle).

Assumptions:

After application of brakes and till the vehicle comes to a stop

- Wheels are fully locked, and

- Brake Efficiency is 100%.




Measurements required in the Braking Test:

a. Braking Distance (L),

b. Initial Speed (u), and

c. Actual Duration of brake application (t).

Skid Resistance (f), f = or f = {a = Retardation, g = 9.81 m/}Actual Skid Resistance, f’ = ηf {η= Brake Efficiency}


DEFINITIONS:

• Traffic Volume: Number of vehicles passing a point or cross section in a given time period.

• Traffic Density: Number of vehicles (in a lane) occupying a unit length of lane at a given instant of time.

• Rate of Flow: Number of vehicles/persons passing a point in a specified time expressed as an equivalent hourly rate (strictly specified as an hourly rate by convention, conversion to hourly rate is necessary for expressing rate of flow).

• Demand: Number of vehicles desired to travel past a point in a lane.

• Capacity: Maximum rate that is achieved in a short span or point during a time period.

Traffic Volume = (Traffic Density) x (Traffic Speed)

TRAFFIC STUDIES

The following fall under the umbrella of Traffic Studies:

• Traffic Volume Studies

• Speed Studies

• Origin and Destination Studies

• Traffic Flow Characteristics

• Traffic Capacity

• Parking Studies

• Accident Studies

TRAFFIC STUDIES

TRAFFIC STUDIES

MID BLOCK

MID BLOCK

INTERSECTION

Mid Block Counts and

Intersection Counts are done separately

• Period of Traffic Volume Studies: Depends on purpose of study

• Time and cost constraints usually demand use of simpler methods of traffic studies.

• Normally used traffic volume study periods: Peak Hour times (Morning or Evening), 12 Hour, 16 Hour, 24 Hour and 7 days.

• Common counting periods for Mid Block Counts:

1 minute, 5 minutes, 30 minutes, 1 hour (usually 5 minutes and 15 minutes durations are preferred). Normally very small counting periods are not desired as they would result in more error in extrapolating the study for a larger data set.

• Common counting periods for Signalized Intersection Counts:

Duration in multiples of cycle length.

TRAFFIC STUDIES

Data to be collected:

• Occupancy Data,

• Turning Moment data,

• Make or type of vehicles.

Challenges in the process:

• Lack of co-ordination among team members,

• Accuracy in information and Data Recording, and

• Organization of data.

Fixed FEILD DATA SHEETS in fixed format are used.

TRAFFIC STUDIES

Planning of Traffic Volume Study:

• Field Sheets should be planned and designed precisely and with clarity.

- Day Date, Time, Location, Turning Moment, Vehicle Type, etc.

- Counting Period (Duration), Total Period (example: 15 min duration for an 8 hour study)

- Climatic conditions

• Personnel should be properly trained

- How and where to use the equipment,

- Vehicle types

- Purpose of study

• Avoid too many enumerators at one place, so as not to disturb the drivers. Aim of study is to get normal data.

TRAFFIC STUDIES

Planning of Traffic Volume Study: cont…

• Choose task distribution, number of personnel, shift change, etc.

• Data recording should be feasible as per human capabilities

• Supervisors should be present on the site

• For ease of team, Mechanical Counters, Pneumatic Counters can be used.

• Pros and cons of both human and mechanical counting techniques should be known and considered.

• Breaks, whenever taken, should be properly recorded in the Data Sheet and suitable extrapolation of data for a continuous trend of traffic movement and volume should be done properly.

TRAFFIC STUDIES

• It includes Laws and Ordinances, Traffic Regulatory Measures (e.g. speed limits) and traffic control devices.

RA FI© PE® TIONS

Traffic Operations

Traffic Regulations

Traffic Control Devices

RA FI© PE® TIONSDRIVER CONTROLSe.g. Issuing driving licences

VEHICLE CONTROLSe.g. Vehicle Registrations

FLOW REGULATIONSe.g. Speed Limits, one ways, etc.

GENERAL CONTROLSe.g. Legal Framework

Traffic Regulations

• DRIVER CONTROLS

Includes Licences, driving tests, financial responsibility (in case of an accident), civil liability (citizens should follow traffic rules)

• VEHICLE CONTROLS

Vehicle registration, vehicle requirements, necessary equipment and accessories, maximum dimensions and weight for loaded vehicles (trucks), fitness of vehicles (engine, brakes in proper condition, etc.)

• FLOW REGULATIONS

Regulations for turning, overtaking, etc. Regulatory signs like one-way, pedestrian control, speed limits, etc.

• GENERAL CONTROLS

Laws in case of accidents, violation of traffic rules (Indian Motor Vehicle Act, 1939)

RA FI© PE® TIONS

RA FI© PE® TIONS

CONFLICTS on a road Intersection

These control, regulate and guide traffic.

Requirements of Traffic Control Devices• Should attract ATTENTION • Should be MEANINGFUL• There should be enough Time To Respond to those signs

Types of Traffic Control Devices• SIGNS• SIGNALS• MARKINGS• ISLANDS

RA FI© PE® TIONSTRAFFIC CONTROL DEVICES

RA FI© PE® TIONS

•Stop & Give way - Prohibitory•Speed Limit - Restriction Ends•Compulsory Direction Control - No Parking

REGULATORY

•RH or LH Curve - Steep Ascent or Descent•Hairpin Bend - Narrow Bridge or road ahead•Reverse Bend - Railway CrossingWARNING•Direction & Place Identification - Parking Signs•Facility Information - Flood Gauge•* Facility: Hospital, Petrol Pump, Food Joints, Resthouses, etc.

INFORMATORY

SIGNS

TRAFFIC CONTROL DEVICES

RA FI© PE® TIONS

TRAFFIC SIGNALSThe crossing streams of traffic are separated by TIME & SEGREGATION.

Alternatively direct traffic to stop and proceed at intersections using Red, Amber and Green lights.

Requirements:

• Draw attention

• Provide meaning

• Time to respond

• Minimum wastage of time

Factors for planning traffic signals• Volume of traffic entering the intersection • Crossing Movements

TRAFFIC CONTROL DEVICES

MARKINGS• Lines, patterns, words, symbols or reflectors on the pavements, kerbs,

sides of islands or surrounding fixed objects within or near the roadway.

• They intend to control, warn, guide or regulate the traffic.

• Their dimensions, colour, contrasts and brightness should be such that they are easily seen/identified by the road users.

• They should be installed or placed at places such that the road users have enough time to react to and follow them.

NOTE:

• Refer the PPT made by Roll Numbers 11 to 20 for road markings. It is a part of your reading material.


The four types of markings are

• Pavement Markings White or yellow lines on roads for division, flow directions like Centre line, lane lines, stop lines, No Passing zone markings, etc.

• Object Markings Markings on Physical Obstructions lying in and near to the traffic flow, like supports for bridges, level crossing gates, traffic islands, narrow bridges, signs and signals, etc.

• Kerb Markings Markings on kerbs and edges of islands, etc.

• Reflector Unit MarkingsUsed as hazard markers and for facilitating night visibility. Visible from a very large distance


TRAFFIC ISLANDSThey are raised areas constructed within the roadway to act as a physical channel through which the vehicular traffic my be guided.

They are classified as

• Divisional Islands (Dividers on roads- facilitate one way traffic)

• Channelizing Islands (at intersections- circular roundabouts, etc)

• Pedestrian Loading Islands (on bus stops (not bus stands))

• Rotary


ChannelizingIslands

The kerb markings are also shown here

Black & White StripsBlack & Yellow Strips

DivisionalIslands

Pedestrian LoadingIslands

Intersections are the areas where two or more continuous lanes cross each other.

Therefore, they act as areas where traffic streams merge, diverge and cross each other.

The probability of accidents are very high on intersections. Both Vehicle-Vehicle conflicts as well as Vehicle-Pedestrian conflicts.

The factors to be considered in design of intersections are:

• Relative Speed (depend on magnitude of velocity of vehicles as well as the angle between the lines of movement of the vehicles)

• Manoeuvre Areas (areas in traffic flow where two or more traffic streams merge, diverge, weave or cross each other)

PLANNING, ANALYSIS & DESIGN INTERSECTIONS

Intersections

Intersections at Grade

Channelized

Unchannelized

Rotary

Grade Separated Intersections

Over-pass

Under-pass

Interchanges

PLANNING, ANALYSIS & DESIGN INTERSECTIONS

Kindly refer Pics circulated on Whats App & e-mails for

Intersections

Or see Fig. 5.34, 5.35, 5.36, 5.37, and 5.39 in

Khanna & Justo

• Increase in the number of vehicles as well as infrastructure (offices, shopping arcades, malls, etc.)

• Absence of proper parking facilities and improper mindset of people results in faulty parking practices which results in congestion, decreased road capacity and increased probability of accidents

PLANNING, ANALYSIS & DESIGN PARKING FACILITIES

PARKING FACILITIES

ON-STREET (KERB)

ANGLE

PARALLEL

OFF-STREET

PARKING LOTS

PARKING DEMAND• The number of vehicles which park at or near to a certain location either

from morning to evening or for some period of time is parking demand for that area/location.

• Methods to compute parking demand• Record the number of vehicles in peak hour duration

Parking Demand = Volume of Traffic Entering – Volume of Traffic leaving the area

(used if parking demand is more than space available)• Count number of vehicles parked at that location w.r.t. time and duration

The count should include number of vehicles parked at different times of the day

along with the duration for which they were parked• Interview people in that area about the parking requirements and parking problems


PARKING CHARACTERISTICS• Study of current parking practices and general problems related to

parking.• Parking patterns (parallel or angle parking) is very important for kerb

parking as it interferes with smooth flow of traffic as well as increases the risk of accidents and also decreases the capacity of the road.

PARKING SPACE INVENTORY• Using the data of parking surveys, a map is prepared for planning places

suitable for kerb parking (along with the parking pattern), for off street parking.

• Balance between Traffic Capacity & Parking Demand is important and necessary for especially metropolitan cities.


ON STREET PARKING

• Parallel parking and Angle parking are decided as per the space requirements available.

• Where the length of parking lot is more, parallel parking is preferred.

• But, if length is not very much, then Angle Parking is preferred. 30˚ Parking is good when Width is less and Length is ok. 60˚ Parking is good when Width is ok and Length is relatively less (but, length is more than the width always, length over here means that it is compared to the requirement).

• 45˚ Parking is optimal from both Length and Width point of view.

• Refer Fig. 5.40


OFF STREET PARKING

• Read about OFF STREET Parking from book.

• Its provided where space is available at lower costs.

• That is why parking lots are in the basement or nowadays the multi-storeyed parking lots are becoming popular due to less availability of land.

• Types of Parking Lots: Self Parking and Attendant Parking (read them from the book)

• Operations in a parking lot

Entrance Acceptance Storage Delivery Exit


PLANNING, ANALYSIS & DESIGN TRAFFIC & TRANSPORTATION PLANNING

Changes in India over the past decade

Traffic Growth

Population Growth

National ProductivityGrowth

Require ImprovementIn Traffic Facilities

Problems

TrafficCongestion

Accidents

Causes

Improper Planning ofRoad Networks and Roadway Facilities

Poor Traffic Planning

TRAFFIC & TRANSPORTATION PLANNING

• Objectives for planning are specified

• Land use and transportation plans are developed

Plan preparation & Evaluation

• Trips between two O&D places are assigned a definite route

• Best route chosen from all routes available e.g. Google Maps- Get Directions

Traffic Assignment• Total

assumed trips are divided between public transportation and private transportation mode

• Socio-economic criterion used for assumption of % division between public and private mode

Model Split

• Trips “generated from” and “attracted from” a zone are distributed to other zones

Trip Distributio

n

• Travel demand Forecasting

• Total Trips from and to a zone are identified

Trip Generation

• Information collected regarding land use, economic activity, population, traffic characteristics and transportation facilities

Inventories

PLANNING, ANALYSIS & DESIGN

• Read/Self Analyse about jobs Divisions of Traffic Engineering units (Field Studies, Accident Analysis, Traffic Control Devices, Design & Planning, Special Investigation, Economic Analysis & Decision Theory in Engg Design and Administration)

• Kindly read the topics of slide 41 from book in detail• Also read about Highway Lighting from book

traffic engineering

Documents

traffic performance

traffic phenomenacontribute

traffic conditionsoptimize

traffic regulation

forecasted traffic

traffic stream characteristics

different traffic situations

traffic situations reactions