Are the sensors the white stripes across the lane? You might look at getting either a thin flat tube and using a fast pressure sensor to detect the wheel contact with a sealed tube, or use a piezoelectric cable, which generates a voltage into a high impedance input proportional to the mass of the wheel. If it is meant to be integrated into the surface then a flexible tube embedded in the top layers, compatible with whatever resin you are using, will give a pressure pulse as the track deforms. A small pulse, but measurable and reasonably accurate time wise.
Otherwise a linear sensor on the central pole and a light source outside the track can be used ( with IR emitters and an appropriate IR filter on the sensor) as a simple sensor, though it will be sensitive to disturbance.