Freeway travel times help drivers know what to expect on the road ahead

Freeway travel times help drivers know what to expect on the road ahead

January 24, 2013

Freeway travel times are displayed on
dynamic message signs throughout the Valley.

Nobody enjoys being stuck in traffic, but depending on the time and location of your daily commute, backups are sometimes tough to avoid.

Just knowing what to expect on the road ahead often eases some of the frustration. That knowledge also allows drivers to make informed decisions concerning their route, which is why ADOT provides freeway travel times…

What are Freeway Travel Times?
If you travel in or around the Valley, you’ve likely seen freeway travel times listed on one of several dynamic message signs – they tell you how long it’s going to take for you to drive from one point to another (15 minutes to I-10, 34 minutes to Warner Road, etc.). You can also find the travel times on

These times aren’t just the result of an educated guess; they’re actually continually being calculated by an automated system that uses traffic data and an algorithm.

James Minton, a shift supervisor at ADOT’s Traffic Operations Center, explains that the system updates frequently as new data comes in from the road.

Embedded detector loops and passive acoustic devices pick up information and send it back to the TOC’s system. Integrated GPS data also is factored into the equation.

From that data, the system computes an average of all travel lanes, which is then automatically displayed on the dynamic message signs.

Interesting fact: The times are very accurate as of the moment you see them on the dynamic message sign. Of course, if a crash or some other type of traffic slowdown happens, there will be an impact on a motorist’s drive time – consequently, the travel time displayed on the dynamic message signs changes based on the impact of the incident.

More Travel Times
ADOT started displaying freeway travel times on several dynamic message signs in the Valley back in 2008 as part of a pilot program.

Since that time, response from the public has been positive. In fact, the travel time displays have been so well received that drivers are now seeing more of them.

Until just recently, there were travel times displayed on 11 dynamic message signs (6 inbound to downtown Phoenix and 5 outbound).

But, within the past few months, more signs have been added. There are now 32 signs total (15 inbound and 17 outbound) giving drivers information on 60 different destinations and about 400 directional miles.

“A lot of people appreciate the system,” said Minton, adding that more expansion is planned for the future as new projects get built. “People have really responded well.”

Human factor
While an automated system does the calculating, ADOT employees are the ones who watch the roads (there are 180 cameras in the metro-Phoenix area alone) and display messages on traffic and road conditions, along with potential alternate routes and other important messages.

Minton and his team also record the travel times each day to spot trends and make sure the system is working the way it is supposed to be.

Active Traffic Management
Assistant State Engineer Reza Karimvand says that being able to display travel time information and messages to drivers is a valuable tool when it comes to managing traffic.

With 106 dynamic message signs in the Valley, there’s big opportunity to share important traffic-related messages with drivers. Not only does the information assist drivers on the road, but the details can actually work to improve traffic.

“If we can divert cars from the scene of an accident, it helps the traffic flow,” he said.