traffic engineering

TRAFFIC ENGINEERING

Definition
Traffic engineering is the science of
 measuring traffic and travel, the study of basic laws relating to traffic flow and generation, and
 application of this knowledge to the professional practice of planning, designing, and operating traffic systems to achieve safe, efficient and convenient movement of persons and goods.

History
 Traffic Engineering as it is known today has evolved gradually with increase in traffic (veh.& ped.)
 Initially it was limited to application of simple rules and regulations such as left driving rule, road signs, marking, and intersection control by flag etc.
 Subsequent analysis of traffic operations and road accidents led to the realization the traffic regulations and other methods of traffic control should be based on proper engineering studies.
 In consequence as extension of traffic regulations - many new traffic control and management techniques were devised viz. speed zoning, traffic signals, turn restrictions, parking restrictions, bus priorities, one-way street etc.
 Eventually it become evident that the planning and design of efficient road network largely depends upon the integrated land-use & transport policies and effective demand management (road pricing to control & distribution peak hours)
 Modern traffic engineering measures are mostly restrictive and dynamic in nature and largely depend on public transport facilities and information technology (IT).

Objectives
 to improve overall roadway capacity
 to ensure safety
 since both vehicle-vehicle and vehicle-pedestrian conflicts reduce roadway capacity and cause accident risk – overall objective is to minimize these conflicts so as to make the most economic use of the existing roadway facilities

Traffic engineering includes
 studies and analysis of traffic characteristics and flow parameters
 geometric design (mainly improvement)
 planning of regulatory measures
 design and application of control devices
 functional planning of road network

Why TE is so essential now-a-days?
Because of
 Increased urbanization process
 Increased traffic demand - phenomenal growth in traffic specially within urban areas
 Difficulties in expanding roadway facilities within built up areas
 Congestion become chronic in every where
 Increased air pollution
 Increased accident numbers
 Road network become larger
Therefore, there is a need to maximize the utilization of existing facilities by better traffic management and control measures.

Bottlenecks - Causes of congestion
For better management of road network, the traffic engineers must know the common causes of congestion and accident.
Causes of Congestion
External (geometric) Factors
 road intersections
 railway crossings
 narrow road/bridge/culverts
 inconsistent roadway width
 poor turning radius
 side frictions
 scattered parking/non-motor activities along road
 frequent side roads entries
 bus stops/parking near junctions
 road side cut/unfinished repair of road side pavement
 poor roadway environment
 poor road discipline
 uncontrolled pedestrian crossing
 poor road surface condition
 speed breaker
 poor sight distance
 poor lighting
 poor drainage facility
Internal (traffic) factors
 heterogeneous traffic stream
 high volume of traffic (demand>capacity)

Safety problems arise mainly from conflicts:
 at intersections
 along on-street parking
 where pedestrian activities are high
 at blind spots - viz. bends, spots with poor sight distance/lighting facilities etc.
due to:
 poor road surface condition
 faulty road geometry
 poor traffic operating condition - lack of traffic control devices
 drivers faults
 mechanical failure

Traffic engineering tools Physical measures
To control vehicular movements
 road signals/signs/markings
 road divider/channelisation/island
 exclusive turning lane - flaring/widening of intersection
 slip road
 bus lay-by
 speed breakers
 segregated bus lane  grade separation etc.
To control standing vehicles
 on/off street parking
 off street load/unloading for freight vehicles  terminals etc.
To control pedestrian movements
 guard rail/median/pedestrian barriers
 side walk
 cross walk
 un-signalized – Zebra crossing
 signalized (time separated/sharing)
 grade separated (space separated)
 underpass
 overpass Regulatory measures
 banning right turn
 one-way operation
 junction clear-way
 speed control
 parking control  access control  road pricing etc.