ADOT puts some of Arizona’s abundant sunshine to good use!

ADOT puts some of Arizona’s abundant sunshine to good use!

August 24, 2011

A top view of the solar panels.

When prices at the pump started to spike a couple years ago, ADOT began looking at ways to cut fuel costs for the 4,200 vehicles in its fleet. And, believe it or not, the idea for a very promising solution came from the roof of a pretend cop car … well, sort of.

Around two years ago ADOT Assistant Director John Nichols was contacted by a company with a new product to demonstrate. It was a stand-in law enforcement vehicle touted as an item that could help ADOT save money. The premise was that it would alleviate the need for a real law enforcement officer at construction sites.

It wasn’t going to work for ADOT, but Nichols had a look and was intrigued by the lights on top of this fiberglass shell of a vehicle. They stayed on even though the car had no engine.

They were powered, he was told, by solar energy and a large pack of lead acid batteries. The solar panels were on the outside of the vehicle and the rest of the mechanism was hidden in the “car.”

It was about this same time that Nichols was involved with ADOT’s efforts to cut fuel costs. In an attempt to find out where fuel-use could efficiently be limited, 117 ADOT vehicles were equipped with a device that provided data on aspects of the vehicle’s operation. It could tell things like average speed, location and even the amount of time ADOT vehicle engines spent idling.

Surprisingly, the data showed that the average vehicle idled about 60 percent of the time it was in use … but with good explanation.

“The reason they idle is because they’re running emergency lighting,” said Nichols, adding when crews are working on the side of the road the lights are crucial to their safety and to the protection of motorists.


Solar-powered emergency lighting is being tested on 50 ADOT vehicles.

The emergency lighting takes a lot of energy to operate and if crews didn’t leave their vehicles running, the lights could kill the battery pretty quickly.

After seeing the solar panels work so well to power lights on the fake vehicle, Nichols wondered if something similar could perform in the same way to power emergency lights on ADOT vehicles and thereby prevent the need for idling and save fuel.

That’s when Nichols asked the company that had come up with the faux police vehicle to work on a solar lighting prototype that might work for ADOT.

“We wanted to test the concept,” Nichols said. “Would solar lighting be able to reduce the amount of idling?”

The company produced a rudimentary prototype and two ADOT vehicles were chosen to test it out – one from maintenance and one from construction.

When the results were in, Nichols says the average idle time went from 60 percent of the time the vehicle was in use, down to 7 percent.

“It was pretty significant,” he said. “That really got our attention.”

But, the prototype wasn’t going to work across the entire fleet. Soon ADOT put out a request for proposals seeking a sleek set-up that would be easy to install and not bulky.

“We challenged the industry … they saw the practicality of this application,” Nichols said.

Eventually a product was settled on to test on a larger scale.

The lights now being tested on 50 ADOT vehicles come with supplemental lithium battery packs that are charged by the solar panels. They also have sensors that can adjust the brightness of the light depending on the time of day. Another bonus is that the new solar lights take only 45 minutes to install. The older non-solar lights take much longer to hook up.

The plan is to try them for an extended period of time, make sure any issues are worked out and then deploy them as standard.

“Our analysis showed they’ll pay for themselves in the first year of use,” Nichols said.