Bus lanes have been widely implemented internationally for improving the performance and quality-ofservice of surface transit systems. Despite their importance to a city’s transit system, bus lanes are frequently violated by road users resulting in subpar service standards. Using extensive field data measurements from Athens, Greece, we analyze violation rates and study their effects on bus lane operational characteristics. Results indicate that: i. reduced perceived enforcement increases violation rates; ii. congestion in adjacent lanes significantly affects bus lane violation characteristics; and, iii. bus speeds are significantly reduced with increased violations.