Methodology
Internal validation programme
- Traffic counting
- Validation
- IRC:64-1990
Measuring our own error, and publishing it
Challenge
Automated counting accuracy can be stated two ways, and quoting only the flattering one is common practice. We wanted a figure that survives an engineer checking it.
Approach
Three surveys were counted by hand, independently, on live uncontrolled traffic — 16,560 vehicles. Software output was compared against those manual counts both by total volume and by weighted per-class accuracy. Categories with fewer than 50 manual counts were excluded as statistically unreliable rather than averaged in.
Outcome
95.0% volume accuracy and 92.1% weighted class accuracy. We publish the weighted figure as the headline because it is the stricter of the two — it does not allow over- and under-counts to cancel.