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Publication Number:  FHWA-HRT-14-059    Date:  August 2014
Publication Number: FHWA-HRT-14-059
Date: August 2014


The Exploratory Advanced Research Program

Use of Vehicle Noise for Roadways, Bridge, and Infrastructure Health Monitoring Workshop Summary Report August 20-21, 2013

Facilitated Discussion

Research Directions

Following the presentations, workshop participants and presenters took part in a facilitated discussion. A summary for each topic of discussion is provided below.

Data Needs

During the discussion, workshop participants suggested that multiple data needs can be addressed. For example, MDOT is creating a fleet to constantly analyze the material conditions and also to collect weather and traffic conditions.

Participants also discussed how trending data over time will allow for learning about degradation over time and what factors contributed to the degradation. In addition, monitoring and trending of data can lead to a better understanding of actionable information, which ties into the DSS. In summary, criteria for actionable information must be defined now and could be improved over time.

Equipment Needs

During the discussion, workshop participants noted that having precise geolocation information is key for data integration—this is not something commercial vehicles currently have. Some participants suggested that an inexpensive GPS unit’s accuracy could be improved toward 3 m (10 ft) by using triangulation; however, triangulation is not considered a reliable method because satellites are turned off intermittently. Participants noted that this method could still have potential if bad data are thrown out, or by referencing data to a base layer that has very high resolution. Moreover, stitching together overlapping acoustical data from a known location could provide precise location data, although this would not be in real time.

Another equipment need discussed included the concept of how using multiple passenger cars provides many measurements of the same segment. A participant noted that hard points, such as manholes or bridge joints, provide references.

A possible starting point, put forward during discussion, is to explore existing passenger and service vehicle controllers. A workshop participant suggested that it is likely that existing controller sampling rates are much lower than what acoustic data require. Existing features, such as anti-lock braking systems (ABS), could be explored further since the technologies are similar in the sense that they are both looking for variations between tires.

As part of this discussion, participants stated that new technologies that could be added to vehicles should be explored now. For example, the DTPS could be installed on any commercial vehicle and is very robust. Participants also noted that likely solutions may be found through a combination of technologies.

Asset Needs

Workshop participants identified two levels of needs during this discussion, as follows:

Participants noted a common reporting metric that can be measured at high- or low-vehicle speed is desired. At present, high-speed IRI measurements are the only industry standard, but this is only applicable for a subset of roads. Distress data, collected at slow speeds, are not as repeatable as IRI measurements, have limitations, and are subjective. Several participants highlighted that the driver for this common metric is to reduce reactive maintenance. One potential solution put forward during discussion is to use a tire pressure sensor to provide IRI or to develop an empirical model to correlate PCI and IRI. A participant noted that PCI should also be improved because it only evaluates the surface of a material. For subsurface information, a map could be produced from sensor data to show the probability of a defect under the surface. Then, issues can be prioritized at a local level for maintenance.


During discussion, participants highlighted that calibration can be performed while driving. Participants noted that data sets can be scaled based on something that is known along the course. Bi-annual or annual calibrations could be performed by using a short test strip. One participant noted that if sensors are applied on all four tires then, during calibration, all four tires should read the same. In summary, participants noted that fixed and mobile sources of data could lead to quality checking. Fixed-point sources already exist and just need to be integrated into the system.

Evaluation Processes and Weather Considerations

Participants suggested that pavement conditions will be evaluated for damage or degradation with results in near-real time by sensing changes in the road between the sensors. Participants noted that this process does not rely on comparing conditions to previous measurements; however, data can be used to observe trends over time. This means that factors, such as weather or seasonal variation, do not impact the process of detecting present damage or degradation.


During the final discussion topic, participants said that engaging manufacturers will assist with successful acceptance of this concept. Participants noted that the key is to decide on equipment and data requirements, and then manufacturers can carry out the implementation. Participants also said that data needs should be discussed widely so that those in other fields, with different motivations for the same data, can assist with the acquisition.


Participants came to several conclusions at the end of the workshop, which are outlined below.

Measurement Considerations

Decision Support Systems

Asset Needs

Potential System Concepts