Percent Reduction in Estimated Vehicular Travel Time in Corridors and Intersections Studied

Measure Description
This measure focuses on traveler benefits derived from vehicular travel time in corridors and intersections studies as a result of re-timing signals along synchronized arterial streets. Travel time is a crucial indicator of how traffic flows along city streets, while also related to levels of fuel consumption and related air pollutants. The Austin Transportation Department's (ATD) goal is to evaluate and retime one-third of the signals annually.
Calculation Method
Travel times are first collected along the synchronized arterials before any timing changes are made. These data along with field observations are used to adjust the signal timing. After all changes are made, the data is recollected. The percent reduction between the before and after travel times represents the average travel time savings travelers could experience when traveling the arterial during peak periods.
FY 2014-15 Results
The FY 2014-15 goal for this measure is a 5% reduction after making signal timing adjustments. Travel times along the corridors studied were reduced by 16%, achieving the goal.
Assessment of Results
ATD evaluated and retimed 161 signals along 15 corridors in FY 2014-15. The rather large reduction in travel time savings indicates that traffic volumes and patterns likely changed since the last times these corridors were retimed. For most of 2010 to 2014, the City of Austin primarily had one signal engineer responsible for retiming the City’s nearly 1,000 signals. To address this, ATD hired three additional signal engineering staff during the latter part of FY 2014-15, and they were available to devote time to retiming and improving coordination among several of those corridors that had not been evaluated in several years. This most likely also led to the much higher reduction in travel times.
ATD employees studying a model roadway
Next Steps
To assist with signal retiming efforts, ATD is pursuing the following:
  • With increased signal timing funding, ATD added an additional staff position in FY 2015-16 who will concentrate on special signal timing projects related to construction and special event activity.
  • ATD is continuing the conversion to a more advanced and innovative signal control system, the Advanced Traffic Management System.
This technology approach will facilitate updating signal timing plans, respond to citizen requests more rapidly, and identify system problems before the public is aware of them.
  • ATD continues to assess signal timing changes in the context of all transportation modes passing through a signal. As a result, changes to signal timing may not show a percent reduction in travel time for vehicles, but there is a direct unmeasured improvement for other modes of transportation. ATD will consider a new measure to determine the overall effect of signal timing changes for all roadway users and vehicles.
  • ATD continues to deploy travel time sensors to allow continuous measurement of both travel time and reliability of travel times along major arterials at all times of the day and not just during the peak period. As a result, a more comprehensive and accurate assessment of performance will be developed.
  • The Transportation Management Center’s hours will be expanded in FY 2015-16 to actively manage the transportation system 24/7 through partnerships with other agencies.
Contact Information
For more information contact Robert Spillar, P.E., Transportation Director at (512) 974-2488.