Analysis of signal flashing at off peak hours

David Mahalel, Ammatzia Peled

Research output: Contribution to journalArticlepeer-review


The decision process for determining the level of control at an intersection must undergo revision to include such aspects as energy consumption and environmental considerations. "Over-control," the prevailing trend in the 1960's, is no longer justifiable in light of present-day concerns - particularly expensive energy consumption by the transport sector and public awareness of environmental quality. Traffic signals, which are the strictest type of traffic control, are warranted for intersections with high traffic volumes, but they are justified neither for low-traffic volumes nor for safety considerations. In addition, traffic signals during off-peak hours effect a disturbance to the normal flow of traffic. A flashing amber operation, in an operational comparison with a regular signal operation, showed a definite improvement in the waiting times of idling vehicles. For high traffic volumes, this ratio was 1:5; for low traffic volumes, 1:13. With the flashing operation, too, there was also an improvement, of 1:2-2.5, the the number of accelerations made by vehicles that stopped before crossing the intersection. The energy saving effected by a flashing amber operation was derived by converting the relative improvement in waiting times and in number of accelerations. The saving was found to be in the ratio of 1:2.5-1:5 for different traffic volumes, ranging from 400-1400 vehicles per hour. Safety evaluation, based on conflict study, showed that for low traffic volumes up to 600 vehicles per hour, the level of safety at an intersection does not deteriorate when a flashing operation is in effect. Shutting down of regular traffic signal operation during off-peak hours for 4 hours per day yields an annual energy saving of more than $16,000 for each intersection, and similarly, an annual saving of 5.5 tons of pollutants.

Original languageEnglish
Pages (from-to)527-540
Number of pages14
JournalCivil Engineering for Practicing and Design Engineers
Issue number6
StatePublished - Jun 1984
Externally publishedYes

ASJC Scopus subject areas

  • General Engineering


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