Distributed acoustic sensing of traffic

Apparatus for estimating a position of a boundary of a queue of traffic, the queue extending along a roadway, comprising:

• an interrogator arranged to generate, as a function of time and of position along the roadway, an acoustic signal representing acoustic vibration at sensing optical fibers that extend along the roadway;
• a composite movement detector arranged to determine, from the acoustic signal, composite movement data representing average traffic speed values of all vehicles for each of a plurality of locations along the roadway;
• a queue signature detector arranged to detect, in the composite movement data, a queue signature of either slowing down of the vehicles as they approach a back boundary of the queue, or speeding up of the vehicles as they advance from a front boundary of the queue by comparing a portion of the composite movement data with queue boundary models, the queue boundary models defining patterns of speed change of vehicles approaching or advancing from the boundary of the queue, and determining that the portion of the composite movement data matches one of the plurality of queue boundary models;
• a queue boundary estimator arranged to estimate the position of the boundary of the queue of traffic from the detected queue signature;
• and
• a road traffic signal controller arranged to, based on the estimated position of the boundary of the queue of traffic, control a road traffic sign to display a warning to traffic that is travelling along the roadway towards the estimated position of the boundary of the queue.

A non-transitory computer readable medium storing instructions that when executed by a processor cause the processor to estimate a position of a boundary of a queue of traffic that extends along a roadway, comprising causing the processor to:

• receive an acoustic signal representing acoustic vibration at a sensing optical fibre that extends along the roadway;
• determine, from the acoustic signal, composite movement data representing average traffic speed values of all vehicles for a plurality of locations along the roadway;
• detect, in the composite movement data, a queue signature of either slowing down of the vehicles as they approach the boundary of the queue, or speeding up of the vehicles as they advance from the boundary of the queue by comparing a portion of the composite movement data with queue boundary models, the queue boundary models defining patterns of speed change of vehicles approaching or advancing from the boundary of the queue, and determining that the portion of the composite movement data matches one of the plurality of queue boundary models;
• estimate the position of the boundary of the queue of traffic from the detected queue signature;
• and
• based on the estimated position of the boundary of the queue of traffic, automatically control a road traffic sign to display a warning to traffic that is travelling along the roadway towards the estimated position of the boundary of the queue.