Table 2 Working specification for instrument.
Parameter | Value | Comment |
|---|---|---|
Minimum detectable absorbance, Amin | 0.01AU (1σ) | Difference after referencing; taken from spectra of aged versus fresh asphalt |
Operating speed in traffic | 20 m s−1 (20,000 mm s−1) | 80 km h−1 |
Averaging time | Up to 0.5 s | Final provision of data over 10 m sections of pavement |
Standoff distance | 20 cm | |
Variation in standoff distance | 5 cm | Without servo control |
1 cm | With servo control | |
Variation in tilt angle | ± 6° | For a 1m wheelbase, the angle for + 5 cm height difference on one wheel and − 5 cm on the other |
Angle of incidence | 15–45° incidence, 0° collection (diffuse) | Possible to reconfigure to determine best geometry experimentally |
Relative humidity | 0 to 90%RH | Not for use in rain; dry roads only |
