At grade rail, in some cases referred to as light rail, often uses rail cars equipment heavier than “Heavy Rail” or subway system rolling stock. The term “Light Rail” generally refers to the relatively light, or lower passenger capacity of the rail cars and light rail trains. Greater weight and mass of rail cars is considered to increase the safety and resistance to collision damage to rail vehicles operating in traffic and crossing multiple streets on the same roadway surfaces and elevations.
Generally operating in a surface street environment, with frequent stopping and starting at station and intersection locations, and nearly constant acceleration and braking along service routes, at grade rail vehicles require constant maintenance and repair. Fixed steel rails are commonly considered to require minimal maintenance or repair. However, because of the frequency of operations and the heavy weight of the vehicles, frequent restoration of the wheels and replacement of the steel rails every few years is necessary, much more often than might be expected. Equipment at crossing gates, stations and street intersections requires the same levels of diligent inspection and maintenance as rolling stock and system infrastructure. The high frequency of maintenance, repair and replacement of parts and components of at grade rail systems leads to an acknowledged economic fact; that rail system manufacturers realize greater profits maintaining rail infrastructure and equipment than are made on the sale of rail vehicles and train components.
Under the daily operational demands of passenger service, at grade rail systems and equipment are subject to greater wear and damage than other transportation systems or technologies. The performance demand placed on equipment and rolling stock of at grade rail systems is likely to shorten the serviceability and longevity of equipment; resulting in more frequent replacement of parts and vehicles. In general, at grade rail equipment is considered to have an anticipated lifetime of about twenty-five years without major restoration or replacement.
Replacement or restoration of the existing rails and roadbed can forestall the use of the system during the maintenance period. In the case of single-track systems, the entire system is affected by maintenance of either the rails or the street surfaces over which it travels. Indeed, the costs of maintenance, repair and replacement of steel wheel, steel rail component parts, rails and train equipment consistently exceeds the cost of the original infrastructure and rolling stock; while monorail systems’ costs and expenses are primarily limited to the original costs of infrastructure development and monorail vehicles.