Adaptive Traffic Signal Control

The Adaptive Traffic Signal Control project upgrades traffic signal technology to optimize signal operation and traffic flow to enable more efficient signal operations and allow real-time adjustments to signals along major traffic corridors.

Page updated on Jun 16, 2020 at 1:03 PM

What is Adaptive Traffic Signal Control?

Alexandria is rolling out intelligent traffic signals that respond and adapt to real-time vehicle location and movement data, optimizing traffic flow, decreasing delays, and reducing stops at various intersections throughout the city.  Currently, the City’s traffic signal system has different types of hardware and software, and some signals can be controlled remotely while other require modification be made in the field.  The Adaptive Traffic Signal Control (Adaptive) project will:

  • Upgrade traffic signal software
  • Implement new traffic signal controllers for consistent infrastructure Citywide and to integrate with future autonomous vehicles
  • Deploy vehicle sensors to allow traffic signals to adapt to changing traffic conditions. 

The existing traffic system works like a programable thermostat implementing synchronization plans based on a time of day schedule.  For example, at 7 a.m. the system will synchronize all the traffic signals for inbound traffic.  Phase I of the Adaptive project will do what the Nest thermostat has done for the home.  Under phase I, traffic signal synchronization will be based on actual conditions and not time of day.  The traffic signals along two corridors, Van Dorn Street and Duke Street, will be placed under adaptive control. Phase II of the project will expand the number of traffic signals under adaptive control and begin the process of harmonize traffic signal control with navigation apps and autonomous vehicles, possibly deploying artificial intelligence, and predicting short term traffic.  

Project Background

The Adaptive Project was initiated several years ago when navigation apps started dynamically changing traffic patterns, reducing predictability.  As travel patterns shift, the old way of synchronizing traffic signals based on the time of day no longer works.  The City applied for and was awarded more than $14.5 million funding to implement this project.  Phase I funding is received through FY21 and Phase II funding begins in FY22.  

Adaptive Traffic Control - Phase I Corridors