Reliability

Miles between Major Mechanical System Failures — Bus

Concepts

These are failures of a mechanical element of the revenue vehicle that prevents the vehicle from completing a scheduled revenue trip or from starting the next scheduled revenue trip because actual movement is limited or because of safety concerns. Examples of major bus failures include breakdowns of air equipment, brakes, doors, engine cooling system, steering and front axle, rear axle and suspension and torque converters.

A number of factors affect the number of major mechanical system failures incurred by a transit agency including local operating conditions, types of vehicles operated, and effectiveness of the maintenance program. However, it is expected that the same types of major mechanical failures will be reported by different agencies. The differences among agencies may be in the numbers reported, not the types of major mechanical failures.

Vehicle miles are the total miles that a vehicle travels while in service (actual vehicle revenue miles and deadhead miles). See the Transit in the United States section for definitions of vehicle revenue miles and deadhead miles.

Comments

Due to changes in the definition of major and minor system failures over the years, only the years 2001 through 2008 are shown in the NTST. Major system failures has decreased 16.4 percent over the last 8 years. Vehicle Miles Between Major System Failures has improved 18.4 percent over the same period.

Figure 33: Miles between Major Mechanical System Failures — Bus 2001 – 2008