We’ve previously shown how and why longer yellow signal times reduce violations and improve intersection safety and that, contrary to the claims of red light camera advocates, drivers don’t adjust to the longer signal times. We now have additional, undeniable proof that we’re right and those supporting photo ticketing are wrong.
In Loma Linda, CA, city officials increased the yellow signal time by 0.3 seconds and saw an immediate 75% decrease in violations from a monthly average of 197 per month to an average of 50 per month. When the yellow time was increased an additional 1.0 seconds, violations decreased a further 92% to an average of 4 per month. The total decrease in violations in Loma Linda was 98% when the yellow time was increased from the original 4.0 seconds to 5.3 seconds. The initial reduction in violations was maintained for three years until the yellow signal time was increased further. The second reduction in violations was maintained for an additional year through the end of the red light camera program in November of 2010 when data was no longer available. That’s four years of longer yellow times with no evidence that drivers adjusted to the longer yellow.
Fremont California has also experienced a significant reduction in violations by increasing their yellow signal time for the straight through movement at the intersection of Mission Blvd. and Mohave Drive. Officials increased the yellow time by 0.7 seconds above the minimum time required by state law to a full 5.0 seconds. As can be seen in the chart below, violations decreased significantly and have remained at the lower rate for almost a full year. Note that the data reflects both straight through and left turn violations but only the yellow time for the straight through movement was increased. Yellow time for the left turn movement remains at the state minimum of 3.0 seconds. It is highly likely that if the left turn yellow time was also increased, the violation rate would be further reduced.
The data above clearly disproves the claim that if you increase the yellow signal time, “drivers will adapt to the longer yellow and still run the red”. Clearly they do not. So the next time you hear someone make this claim, point them here, and show them proof that they are simply wrong.
*All violation data was obtained through public records requests of the cities of Loma Linda and Fremont. Special thanks to Jim at HighwayRobbery.net and Roger Jones, for obtaining the data used in the above charts.