With more than 6,000 miles of highway to oversee and maintain, ADOT relies on its fleet of trusty vehicles to help get the job done. We’re not referring to your everyday trucks and sedans – we are talking about heavy-duty equipment, designed and built to perform some enormous tasks.

Because these vehicles play such an integral role in ADOT’s everyday operations, we thought it’d be fitting to highlight some of them here on the blog.

So, let’s get things started by introducing you to ADOT’s bucket trucks…

Extending up to 45 feet, these trucks are used primarily by ADOT’s Signal and Lighting crews to repair and maintain traffic signals and lights.

The bucket truck is used to repair traffic signals, freeway lights (the shorter poles) and the lights that shine underneath bridge decks.

The bucket trucks have compartments used for supplies.

By the way, there is also a larger bucket truck available that’s used to work on the taller freeway light poles – it reaches 68 feet.

Before an ADOT crew member can get in the bucket and head on up, they have to stay safe and put on a full-body harness and a hard hat. Also, before the bucket will elevate, a couple of stabilizers extend out of the sides of the truck (kind of like hydraulic kick stands) to keep things nice and steady.

Another safety factor – two crew members go out with these trucks. One person operates an arrow board/attenuator truck (to warn traffic) and one will be up in the bucket making repairs to the light or signal.

One more thing about these trucks is that they have several compartments that allow crews to carry along all the supplies necessary to make a repair.

You can learn more about ADOT’s Signals and Lighting crews, by reading some of our previous posts. And, be sure to stay tuned for upcoming blog posts about the Vehicles of ADOT.

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.

Nothing seems to slow a commute down like having to stop at one red light after another …

That’s why ADOT is working to synchronize some of its signals – a move that can help traffic flow a little more smoothly while reducing the type of stop-and-go traffic that can lead to congestion.

But wait … maybe you’re wondering how many traffic signals ADOT really has to worry about.

It’s true, this is the agency responsible for building and maintaining highways … and you don’t see any traffic lights out on the freeway. But you will encounter ADOT lights at freeway off-ramps and there are several state roads that have traffic signals.

Take Grand Avenue (US 60) for example … there are several lights on this stretch of road. Just last month ADOT worked to synchronize, or coordinate, the timing of the signals on Grand Avenue to reduce the number of stops that drivers make at red lights (maybe you’ve noticed a difference?).

The signals are synched to improve the flow of southeast-bound traffic during weekday morning commutes and to assist northwest-bound traffic during the afternoon.

ADOT is working with the cities of Phoenix, Glendale, Peoria, El Mirage, Surprise and Youngtown, as well as Maricopa County, on the project to coordinate traffic signal timing at a total of 36 Grand Avenue intersections.

Besides Grand Avenue, ADOT has signalized roads throughout the state including Route 66 in Flagstaff, Prescott Valley’s SR 69 and Tucson’s SR 77 … and they’re all synched.

To learn a little more about traffic signals and ADOT, we talked with ADOT Phoenix Maintenance District Engineer Tim Wolfe – he gets lots of questions about signals. We thought we’d share some of the most common questions along with the answers …

What speed should I drive to hit the green lights?
Wolfe says ADOT signals are synched to match the posted speed limit. In the case of Grand Avenue, that’s 45 mph.

How do the traffic signals know how to keep time with each other?
According to Wolfe, all the signals have a GPS clock installed. In the middle of the night each signal “talks” to the world clock and resets itself so each signal is exactly the same time.

If I miss a light, how long do I have to wait for the next green?
Wolfe says at the most you’ll be waiting half a cycle. A typical cycle is 90 seconds. On Grand Avenue it’s 130 seconds and in some places on Grand Avenue in Phoenix where there are six-way intersections, the interval is 210 seconds. So if you miss the green on Grand, expect a wait of anywhere from 45 seconds to 105 seconds depending on your location.

What sort of a difference does signal coordination make?
ADOT employees drove Grand Avenue before and after the signal synchronization in a vehicle equipped with a GPS device. They’ve gathered all the data and are analyzing it to get a precise look at the impact, according to Wolfe. However, even without the official numbers, Wolfe says drivers are noticing significant improvements on Grand Avenue.

If you drive Valley freeways during rush hour, you’re probably pretty familiar with ramp meters …

They’re the two-light signals positioned at most Valley on-ramps that tell motorists when it’s okay to head onto the freeway.

Ramp meters have been used in the Phoenix-Metro area for about the past 20 years and maybe you think not much about them has changed … but, actually they’ve recently become much more efficient!

Thanks to a project funded through the Maricopa Association of Governments (MAG), roughly 300 ramp meters have been replaced with units that use newer, smarter technology.

As ADOT’s Intelligent Transportation System Supervisor Chuck McClatchey explains in the video above, the older ramp meters were not nearly as efficient as the new models.

“The new controllers actually operate totally independent of each other, which, means you can have 15 cars in one lane, no cars in the other lane and it will give 15 straight greens and just maintain red on the left side,” he said. “The older technology would give two greens and then a green to the non-existent cars. … So you can see that it really was not that efficient.”

But how does the ramp meter “know” a car is ready and waiting to take off onto the freeway?

Well, there are actually sensors in the ground adjacent to the signals that can detect a car as it pulls up. The ramp meter will then give a green light and start metering back and forth between the two lanes.

The meters also get information from the mainline, or freeway.

If the mainline is free-flowing, then the ramp meter will put on as many cars as possible. But if the mainline traffic slows down, the sensors pick that up and the rate at which cars are given a green light slows down some to help relieve the congestion.

The system has something called a queue-loop located at the very top of the ramp, too. The queue-loop is kind of a manual override that senses when traffic is backed up on the ramp completely up to the top. If that happens, the loop is activated and the metering goes to the fastest rate until the ramp is cleared. Basically, it’s a safety factor that keeps traffic from backing up into the surface street intersections.

All these features add up and help make it a little easier for motorists to get where they need to go!