- IR camera's "integration time" (typically >10 ms).
- The faster the speed, the more the image is blurred (a vehicle at 60 mph moves almost 0.9 ft. in 10ms).
- Low speed method requires a rolling lane closure
- Higher speed would have some advantages
- No closures (safer)
- Lower cost
- Higher production rate
As a result, several agencies have specified high-speed IR and a number of high-speed projects have been carried out by Infrasense and others.
- Michigan DOT (11 decks, 2015)
- Wyoming DOT (32 decks, 2015)
- Nevado DOT (Las Vegas viaduct, 2015)
- Colorado DOT (15 decks, 2014)
How good are the results? When is it appropriate to do high-speed vs. low speed?
Infrasense has tested the effects of speed on the quality of the IR data
Typical Corresponding Visual and IR Data Frames at Low Speed
IR Images vs Speed - Patches under an AC Overlay
IR Images vs. Speed - Deck Delaminations
Summary of findings:
- Low speed provides more detailed delineation of delaminations
- When delaminations are clear in the IR data, high speed and low speed results match reasonably well
- When delaminations are not as clear (as occurs with overlays), high speed data is harder to interpret (based on project experience)
- High speed does not allow for confirmation sounding
Conclusions - Low-Speed vs. High-Speed
- Low-Speed is a preferred option for:
- Project level evaluations and mapping of repairs
- Low-speed, low-volume roads
- Decks with concrete overlays
- High-Speed is a viable option for:
- Network level evaluations
- High-speed, high-volume roads (no closures)
- Decks without overlays