Individual Vehicle Speed Estimation Using Single Loop Inductive Waveforms

Problem and Method

The method developed as part of this research was found to perform better than other previously developed single loop detector methods of estimating speed. This is in part due to the fact that unlike the earlier methods, the method developed in this research estimates speed independent of vehicle length assumptions.

The ability to utilize the current loop detector infrastructure to obtain reasonably accurate estimates of vehicle speeds may save considerable cost and traffic delay associate with the construction of new loops. However, double-loop speed measurement methods ("speed traps") are still necessary if high accuracy in speed computation is required.

Findings

This research sought to develop a new method to estimate vehicle speed using a single loop detector rather than a "speed trap" setup in which two loop detectors are used in sequence.

Prior to this research, methods were developed to estimate vehicle speed using a single loop detector. However these methods are dependent on an assumption of vehicle length distribution, which leads to biased results for individual vehicles outside the assumed vehicle length (such as trucks and motorcycles).

This research developed a speed detection algorithm that analyzes the waveform generated by vehicle passing over a single loop detector and estimates the speed of the passing vehicle independent of the vehicle length, leading to more accurate speed estimation than previous single detector methods.