When the Pennsylvania Turnpike Commission pledges to go the extra mile for its customers, that includes a safe and comfortable ride. In order to keep that promise, Turnpike engineers rely on some very specialized help from the Pennsylvania Department of Transportation (PENNDOT), who perform specific pavement tests using highly sensitive equipment on the entire 506-mile Turnpike.

Turnpike Executive Director of Engineering and Maintenance/Chief Engineer Alexander R.Jansen said, "The Turnpike's Pavement Surface Quality Committee (PSQC) adds the information we receive from PENNDOT to the findings of our own engineers in order to prioritize rehabilitation projects on the Turnpike."

PENNDOT's sophisticated testing equipment is housed in two specially outfitted vehicles that are designed to test the road's surface for the ability to brake on wet pavement (friction testing), a smooth ride (roughness testing) and ruts (profile testing) on the highway.

Larry Stultz, PENNDOT's Roadway Program Technical Supervisor, explained: "The pickup truck is equipped to test for friction. This shows us where the highway has become too smooth from long-term wear. If the road's surface is too smooth, it can become slick when it rains, and therefore can hamper motorists' ability to brake." To keep sections of the Turnpike from becoming slick, they are resurfaced with a course aggregate mixture specifically designed to preserve traction.

The $183,000.00 friction truck and attached trailer is a modern marvel, loaded with an International Cybernetics Corporation computer system and a tank containing 300 gallons of water. Untreaded tires, manufactured for test purposes only (at a price of $350.00 per tire) are mounted on the trailer.

Driving the truck at up to 40 miles-per-hour, Stultz releases measured amounts of water (about 28 gallons per minute) onto the highway, allowing untreaded tires to drag and skid on the wet pavement. "We allow at least five skids per mile," Stultz said. "Measurements of the skids are immediately registered on the computer screen which is installed between the driver and passenger seats."

Rough spots and ruts along the highway are tested with PENNDOT's $170,000.00 state-of-the-art van. Results of the International Roughness Index (IRI), a standard international measurement, eventually translate into a smoother ride for Turnpike customers.

Resurfacing the roadway occurs before rutting becomes serious enough for motorists to feel it in their steering. Elimination of the ruts also reduces the chance for hydroplaning. "The van is equipped with lasers that take a reading of the roadway every six inches," Stultz explained. "A laser beam no larger than the lead of a pencil, and an ultra sonic sensor analyzes each section of the roadway. This information is relayed back to the computer, telling us where the pavement has become too rough, or that rutting has occurred."

The two PENNDOT vehicles travel the Turnpike for approximately two weeks every other year. In order to alert Turnpike drivers, the trucks are equipped with flashing lights. Tests are only made in the summer, when ice and snow can't hamper the procedures.

The testing begins at the Harrisburg-East Interchange (Exit # 19) and proceeds east to the Delaware River Bridge, then turns and travels up the Northeastern Extension. The vehicle then returns to Harrisburg and proceeds west to complete the testing from the Harrisburg-East Interchange to the Gateway Interchange at the Ohio state line.

The Turnpike uses PENNDOT's test vehicle instead of purchasing its own because it is not cost effective. John Hickey, Turnpike Research Manager, noted: "PENNDOT already tests every state-owned road in Pennsylvania every two years, and interstates and other priority roadways more often. They keep this equipment busy enough to justify the cost of purchase, upkeep and crew training. Testing the entire Turnpike takes less than two weeks, so we can't justify such a large expenditure."

Turnpike Executive Director John T. Durbin remarked, "A team of Turnpike engineers perform inspections twice a year. We use PENNDOT's results in addition to our own figures for more exact detail and comparisons and, most importantly, to help ensure the safest and most comfortable ride possible for Turnpike customers."

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