A consistent and fast response time is crucial for accurate speed measurements. Response time is affected by vehicle size, speed, detector type, sensitivity, and wire type. Response time decreases with smaller vehicles, which have lower ground clearance and a shorter distance to the engine block and axle. Faster speeds tend to reduce response time, as does increased sensitivity. Recovery time - the time required for a loop to return to normal operation after a period of sustained occupancy.
Recovery time is particularly important for vehicle counting.
Loops should also be stationed around access and egress points, and at any locations where operational problems occur. Provisions should also be made for maintenance access. Different degrees of processing of raw loop data may be performed at the TMC or remotely in the field. If transmission lines are leased, which is often the case, data transmission costs can become cost prohibitive. Loop detectors are relatively inexpensive.