The total number of miles traveled by passengers on transit vehicles. Passenger miles are a measure of service utilization, which represents the cumulative sum of the distances ridden by each passenger. For example, ten passengers riding in a vehicle for two miles equals 20 passenger miles. Passenger miles can be actual numbers or can be determined by multiplying the number of one-way trips times the average length of a passenger one-way trip. Passengers per mile is an effectiveness indicator which measures service utilization. A higher number is more favorable. Service area characteristics and service design impact this indicator. For example, a transit system serving a community with a widely dispersed population must operate less efficient, circuitous routes that tend to carry fewer passengers per mile.