Arizona's highways rank among nation's 'smoothest'

A baby’s skin. A gifted speaker. Arizona’s roads. What do these three, far-different things have in common?

The answer is smoothness, and Arizona has the data to back up its placement in the comparison.

According to a recent Federal Highway Administration evaluation, Arizona ranks among the top five states in the U.S. in the percentage of vehicle miles traveled on good-riding pavements (think smooth roads) on the national highway system, or NHS. The evaluation was based on six-years of NHS pavement performance data.

The state also achieved one of the five highest percentage increases in vehicle miles traveled on good-riding pavements, going from 73 percent six years ago to 85.8 percent today.

ADOT’s Smooth Operators
Who are the smooth operators responsible for these results?

Tom Deitering, an area engineer and pavement and materials coordinator for FHWA’s Arizona Division, gives much of the credit to ADOT’s Pavement Management System.

“I believe there are many reasons for these high scores, but my first thought was the great strides that ADOT has made in the Pavement Management System over the last several years,” Deitering said in an email. “[T]he system has grown in its sophistication, and it allows ADOT to stay well tuned with the condition and needs of the pavements in the state.”

Bill Hurguy manages the Pavement Management Section, a 12-member team that monitors the conditions of the pavements making up Arizona’s highway system. One of the section’s duties is measuring smoothness.

The section operates two vans, each equipped with a sophisticated instrument called a profilometer that works in concert with an onboard computer system to measure the smoothness of roads. The equipment samples a road segment every mile while the van travels at normal highway speeds.

The two most common ways to define roadway smoothness are the International Roughness Scale, or IRI, and the Profilograph Index, or PRI.

All states collect and report their smoothness data to the Federal Highway Administration’s Highway Performance Monitoring System, or HPMS. In turn, the FHWA uses this data to determine the ride quality of the roads in each state.

Numerous studies have shown that most drivers judge the quality of a road “good” or “bad” based on its smoothness. Other studies point to the benefits that smooth roads bring in terms of pavement longevity, motorist safety, and reduced vehicle operating costs. When you’re driving on rough roads, more wear-and-tear is caused to vehicles and it can make for a noisy and uncomfortable rise.

Reasons for Success
Hurguy acknowledges his section’s contribution, but he points out that success is due to a combination of factors and teamwork. “In the end, all we do is measure the smoothness; the smoothness is a result of many factors.”

Those factors include contractor incentives, frequent use of rubberized asphalt as a top layer of a road, collaboration with pavement designers and contractors, and maintenance activities.

The department offers contractors incentives to build smoother roads, whether for new construction, reconstruction, or rehabilitation projects. If the contractor exceeds established target values, it can earn a bonus averaging around $80,000. But it goes both ways – occasionally, contractors are charged for not meeting target values. The Pavement Management Section members periodically meet with the contractors to review target values and discuss if they are meaningful and realistic.

“It’s a good opportunity for contractors to make additional money,” Hurguy said of the incentive program, a notion that FHWA’s Deitering agrees with.

“It’s caused the contractors, on their own, to institute construction techniques to increase smooth pavement,” Deitering said. That innovation pays off for Arizona taxpayers through longer-lasting roads.

A Road Most Traveled
Finances help too. Allocations for pavement preservation have increased 35 percent over the past five years. For example, $135 million has been budgeted for pavement preservation for Fiscal Year 2011. This investment helps to extend the usable life of pavement, avoiding more expensive total replacement.

“Our maintenance people are a major reason why we have such smooth and long-lasting roads,” Hurguy said. The crews regularly take actions to care for the pavement, including crack sealing, patching, and even controlling the vegetation and keeping the ditches clean. “Everything that they [maintenance crews] do helps.”