Introduction to Traffic Engineering

1. Introduction to Traffic Engineering BY: ALAMEREW M.

2. Objectives of this chapter • Help students lay solid foundation of traffic engineering as a whole • Help students get general knowledge of traffic engineering from both theory and practice • Lead students to traffic/transportation professional world

3. 1.1 Definition, scope and goal Definition of Traffic Engineering --- It is the phase of transportation engineering that deals with the planning, geometric design and traffic operations of roads, streets and highways, their networks, terminals, abutting lands, and relationships with other modes of transportation

4. Transportation Engineering is defined as a discipline applying technology and scientific principles to the planning, functional design, operation, and management of facilities for all modes of transportation

5. Scope of Traffic Engineering --- surface (land) transportation; relationships and connection with other modes of transportation • Major modes of surface transportation --- automobile, bus, truck and bike

6. Goal of Traffic Engineering --- explore how to provide for the safe, rapid, comfortable, convenient, economical, and environmentally compatible movement of people and goods. • Safe --- public safety • Rapid --- time value and customer service • Comfortable/convenient --- level of service • Economical --- social cost • Environmental --- clean air and sustainability • Movement = mobility

7. Capacity and level of service analyses The no. of vehicles on our highways increases every year and transportation engineers are often faced with the challenge of designing modifications to existing facilities that will service the increased demand.

8. Capacity: is the maximum no. of vehicles that a given highway can accommodate. • LOS: is an operating condition under capacity. Traffic engineers use capacity & LOS analysis to: • Determine the no. and width of lanes needed • Assess service levels and operational characteristics of existing facilities. • Identify traffic and roadway changes needed for new dev’t.

9. LOS A Free-flow operation LOS B Reasonably free flow Ability to maneuver is only slightly restricted Effects of minor incidents still easily absorbed Levels of Service LOS concepts Highway capacity manual defines the LOS categories for freeways and multilane highways as follows: From Highway Capacity Manual, 2000

10. LOS C Speeds at or near FFS Freedom to maneuver is noticeably restricted Queues may form behind any significant blockage. LOS D Speeds decline slightly with increasing flows Density increases more quickly Freedom to maneuver is more noticeably limited Minor incidents create queuing Levels of Service From Highway Capacity Manual, 2000

11. LOS E Operation near or at capacity No usable gaps in the traffic stream Operations extremely volatile Any disruption causes queuing LOS F Breakdown in flow Queues form behind breakdown points Demand > capacity Levels of Service From Highway Capacity Manual, 2000

12. LOS determination Base condition: * lane width * terrain * lateral clearance * traffic condition stream * access frequency * driver population characteristics Steps: • Measure Free-flow speed from the field-is the mean speed of traffic as measured when flow rates are low to moderate • Analysis flow rate –the highest volume in a 24-hr (the peak-hr volume) is used for V in traffic analysis computation. • Determine LOS