"Route miles" refers to the total length of a specific transportation route, such as roads or railway lines, measured in miles. It measures the distance covered by a particular path or route. Full definition
Taking overall track length into consideration, the San Diego Trolley transported 2,239 daily passengers per route mile in Q4 2014, making it the twelfth busiest Light rail system on a per mile basis over this time period. (en.wikipedia.org)
[37] The Trolley system's highest average weekday ridership of 124,300 was achieved in Q3 2007 [38]-- this corresponded to 2,323 passengers per route mile daily. (en.wikipedia.org)
BNSF Railway is one of North America's leading freight transportation companies which operates approximately 32,500 route miles of track in 28 states and in three Canadian provinces and transports consumer goods, agricultural products, coal and industrial goods. (naiop.org)