Traffic Signal Preemption

In Traffic Signal Preemption, you'll learn ...

• The detector location for emergency vehicles
• The detector for priority transit vehicles
• Traffic signal phasing used to clear the tracks of vehicles
• The signal sequence during preemption operations

Overview

Credit: 4 PDH

Length: 45 pages

This course explains the main types of traffic preemption methods used for emergency vehicles, bus and light-rail priority, and traffic signals at, or adjacent to, highway-rail grade crossings. These preemption methods override traffic signals in order to improve the operational schedules of transit vehicles, facilitate the movement of emergency vehicles, or restrict vehicles from crossing railroad tracks.

Each preemption program has to conform to the roadway conditions and account for adverse affects upon the existing traffic pattern. Therefore, traffic engineers must understand that changing the sequence of phases, timings, and cycle lengths will have dramatic consequences on existing traffic patterns. We will discuss the relevant factors pertaining to bus priority systems, emergency vehicles preemption, highway-rail grade crossings, governmental regulations, the preemption problem, traffic signals at highway-rail grade crossings, tell-tale lights, and pedestrian and driver impatience.

We will also analyze the different methods used to place traffic controllers into priority or preemption mode and determine the duration of that mode, as well as the methods used to integrate the traffic signal phasing and timings back into the existing signal program. This course will help you understand the design and operation of traffic signal preemption modes as they relate to phase sequence options and signal display options, which are used to obtain the desired preemption modes at an intersection.