Roadway signs have a finite life span. Exposed to the ravages of time and weather, they gradually but steadily lose their retroreflectiveness and, thus, their effectiveness.
To minimize the risk of traffic accidents, the West Central Indiana Economic Development District used $175,000 in FHWA Highway Safety Improvement Program (HSIP) funding to build a GIS database of Vigo County’s 31,000 signs. Although the 410-square-mile county includes Terre Haute and other mid-size cities, some of its 1,250 miles of roadway are rural.
The project was also necessary to ensure compliance with a federal mandate. A 2009 revision to the Manual on Uniform Traffic Control Devices (MUTCD) requires public agencies to implement an assessment or management method for maintaining retroreflectivity at or above established minimum levels.
The development district had a RoadVista 922 retroreflectometer, manufactured by Professional Pavement Products Inc. of Jacksonville, Fla. The unit is held directly against the face of a sign, enabling crews to work during the day rather than at night. But the department lacked two other critical components: the physical position of each sign and the ability to merge that data with its retroreflectivity values.
“It was a challenge, but we thought we could do it in about three months,” says Matt Healy, survey manager for VS Engineering Inc., which was retained to solve the challenge. Founded in 1980, the Indianapolis consulting firm uses cutting-edge technology to develop common sense solutions for all phases of municipal civil, transportation, environmental, structural, surveying, and traffic projects.
Change in direction
The timeline was seriously impacted, however, by the retroreflectometer. VS Engineering had done similar projects, but none involved quantifying reflectivity. While great at its job—measuring reflectivity—using the device in the field took longer than anticipated. And it didn’t provide all of the required data.
“The retroreflectometer was giving us solid measurement performance, but one of its built-in functions, assigning a sequential number to each sign, wasn’t,” Healy says. “Fairly well into the project, it began to skip numbers, throwing all of our work up to that point into question.”
The firm initially hoped to simply keep track of each sign number, enter it into the GIS as an attribute, and then merge it with the location data. But with the accuracy of the sequencing thrown into question, the database had to also note whether or not a sign met required minimal retroreflectivity values.
VS Engineering uses the GRS-1, a hand-held GPS unit with built-in Bluetooth and wireless LAN capability manufactured by Topcon Positioning Systems Inc. of Livermore, Calif., for mapping. During training sessions, the Professional Pavement Products representative had mentioned several customers were using hand-held Bluetooth-enabled GPS units in conjunction with the RoadVista retroreflectometer.
Unsure how long it might take to blend the two technologies into a single compatible system, Healy reached out to Topcon GIS Sales Manager Jason Hooten. In less than three weeks, the manufacturer wrote software integrating the retroreflectometer with the GRS-1, as well as with the Topcon Tesla field controller Healy bought for the project.
“That gave us everything we needed to create our database,” he says.
A workable solution
In its final form, retroreflectometer barcode and background and legend readings are now automatically entered into the appropriate data fields in the eGIS (Topcon’s proprietary software) database. The integration allows the resulting field data to be stored into the shapefile without additional manipulation. For the end-user, this means data can be used in GIS queries immediately upon receipt in the office.
Once completed, the database will be hosted by the development district but owned and shared by all of the towns and municipalities within the county.
With the two technologies now working in tandem, Healy’s team attacked the project in earnest.
The GRS-1 captures latitude and longitude to less than 1 meter, so the first thing they noticed was the degree of positional accuracy over using just the retroreflectometer.
“I was confident that 80% of the time, accuracy fell within the footprint of the user recording the position,” Healy says. “We’re still using two separate pieces of equipment, but the integration ensures that no data from either one is lost when merged.”
