Results of signal coordination show big improvements

ADOT’s efforts to ease some of the stop-and-go traffic on Grand Avenue have been pretty successful so far, but you don’t have to just take our word – we’ve got the results to prove it!

Before we reveal those findings, let’s back things up a bit first … 

You may recall this blog post from a few weeks ago. In it we described how ADOT worked with the cities of Phoenix, Glendale, Peoria, El Mirage, Surprise and Youngtown, as well as Maricopa County, on a project to coordinate traffic signal timing at a total of 36 Grand Avenue intersections.

The signals were synched, or coordinated, to improve the flow of southeast-bound traffic during weekday mornings and to assist northwest-bound traffic during the afternoon.

Basically, the idea was to reduce the number of red lights drivers come across during their rush-hour commutes.

Drivers may have quickly noticed the difference, but ADOT wanted to quantify those results and measure how much of an improvement was made. A study on the corridor just wrapped up and judging by the results, it seems the impact has been considerable.

In fact, the average travel time has been reduced by 15 percent in the morning (for traffic heading southeast) and 20 percent in the evening (for motorists driving northwest). That equates to a roughly seven-minute saving for commuters who drive the entire corridor in the morning and a ten-minute savings for afternoon drivers!

On top of that, the average number of stops for a driver traveling the entire corridor was reduced from roughly 16 to 10 in the morning and from 21 to 9 in the afternoon. The study also shows that motorists in the morning and evening experienced an average increase in speed by about five miles per hour.

In addition to the time savings, the study found that vehicles saw decreases in fuel consumption and emissions.

How the study was conducted 
Data was collected both before and after the Grand Avenue signals were coordinated. ADOT consultants did this by completing six travel time runs in both directions (northwest and southeast) during the morning, afternoon and evening peak traffic periods.

All the measurements were taken on Tuesdays, Wednesdays and Thursdays over a two-week period. The “before” times were taken in October/November and the “after” times were recorded in mid-January.

To complete a travel time run, test drivers started at one end of the corridor and drove all the way to the other end. To ensure the cars were essentially traveling the median speed, drivers were instructed to pass one vehicle for each vehicle that passed them.

In order to gather the data, each car was equipped with a GPS device (smart phone or tablet). The GPS data was recorded using an application designed for calculating travel time information.

ADOT Phoenix Maintenance District Engineer Tim Wolfe says the project and study proves signal coordination can make a significant difference.

“We were certainly pleased by the improvements,” Wolfe said.