Small Business Innovation Research Program

Public Roads, March-April, 1998 by Charles W. Niessner

One of the early SBIR projects developed a retroreflectometer that uses the principle of retroreflection and a scanning laser beam to measure the retroreflectivity of lane markings. Retroreflectivity is vital, particularly at night, for effective pavement markings that aid efficient traffic flow, driving comfort, and highway safety. The retroreflectometer is mounted on the outside of a van, and entire sections of pavement markings can be evaluated as the vehicle travels at speeds of up to 88 kilometers per hour. A computer inside the vehicle collects, formats, stores, and outputs the data. The retroreflectivity data is available for analysis almost immediately after measurements are taken. This new technology gives highway officials a tool for the nonsubjective, repeatable measurement of retroreflectivity of pavement markings. The device is currently being promoted as part of a demonstration project by FHWA's Office of Technology Applications.

Another project developed improved equipment for the consolidation of concrete pavements. This equipment relies on a harmonic combination of internal and surface vibrations and uses the resonance phenomenon to optimize the efficiency and consistency of consolidated concrete pavements. The system also allows for quantitative assessment of the consolidation conditions. This equipment produces stronger, less permeable, more uniform concrete pavements. It also requires less maintenance than current equipment, and as a result, the life-cycle cost of the new system is about 40 percent less. A major equipment manufacturer will produce the equipment, and it will be available on new pavers or can be purchased to retrofit existing pavers.

In monitoring vibrations in highway structures, it is desirable to collect data from many points on the bridge. However, the sensors must be wired to a central location. This is not only costly, but it requires long cables, which are susceptible to interference that can degrade the data quality. A solution is to collect sensor data by radio. The system developed under this SBIR project offers the means to instrument a bridge with either strain gauges or accelerometers to assess structural performance. The key advantage is the elimination of cables, thereby drastically reducing the cost of such instrumentation.

The system consists of 10 remote modules - each capable of monitoring four data channels - and one base module connected to a portable computer. The technician can place the remote nodes right at the instrumentation site, and a telemetry relay is then established to a local base site. The system has undergone field trials at the Woodrow Wilson Bridge (I-95, the Capital Beltway, over the Potomac River south of Washington, D.C.) in March 1995 and again at a bridge site in New Mexico in November 1995.

The system is ideally suited to load-rate bridges based on measured data. The use of real data provides a more accurate load rating, but it is not usually done today because the cost of "wiring" a bridge is prohibitive. The system is also an excellent research tool.