Modern machinery enables a small group of workers to maintain a relatively long stretch of railroad track. Machines are available to do all the necessary track maintenance tasks: removing and inserting ties, tamping the ballast, cleaning the ballast, excavation and replacement of worn ballast, spiking rail, tightening bolts, and aligning the track. Some machines are equipped to perform more than one task—for example, ballast tamping combined with track lining and leveling. Mechanized equipment also can renew rail, either in conventional bolted lengths or with long welded lengths; a modern machine of this type has built-in devices to lift and pass the old rail to flatcars at its rear and to bring forward and deposit new rail, so that it dispenses with separate crane vehicles.

Complete sections of track—rails and crossties—may be prefabricated and laid in the track by mechanical means. Rail-grinding machines run over the track to even out irregularities in the rail surface. Track-measurement cars, under their own power or coupled into regular trains, can record all aspects of track alignment and riding quality on moving charts, so that maintenance forces can pinpoint the specific locations needing corrective work. Detector cars move over the main-line tracks at intervals with electronic-inspection apparatus to locate any internal flaws in the rails.

The mechanization of track maintenance after World War II has constituted a technologic revolution comparable to the development of the diesel locomotive and electrification. Precision of operation, especially in maintenance of true track alignment, has gained much from the application of electronics to the machines’ measuring and control devices. In Europe in particular, highly sophisticated maintenance machines have come into use.

Bridges

The designer of a railroad bridge must allow for forces that result from the concentrated impact that occurs as a train moves onto the bridge; the pounding of wheels, the sidesway of the train, and the drag or push effect as a train is braked or started on a bridge. These factors mean that a railroad bridge must be of heavier construction than a highway bridge of equal length.

As axle loadings become heavier and train speeds higher, bridges need to be further strengthened. Another major objective in modern railroad-bridge construction is the need to minimize maintenance costs. The use of weathering steel, which needs no painting, all-welded construction, and permanent walkways for maintenance personnel contribute to this end. In the advanced countries there has been a widespread trend toward reinforced concrete structures.

Buildings

Railroad buildings have become fewer and more functional. With paved highways running almost everywhere in the developed countries, it has become more economical to concentrate both freight and passenger operations at fewer stations that are strategically sited and have good highway access. Provision for intermodal traffic exchange has become increasingly important. Particularly in conurbations, the forecourt and surroundings of new passenger stations are laid out to provide adequate and convenient areas for connecting bus or trolley-car services, for private automobile parking, or for so-called “kiss-and-ride”—automobiles that are discharging or picking up rail passengers. Many existing stations have had their surroundings reorganized to provide these facilities.

Many new local stations have been built to serve the spread of commuter and rapid-transit rail systems. However, except on high-speed intercity lines, or at some airports, few sizable city stations have been newly constructed. On the other hand, there has been major reconstruction, updating, and expansion of facilities within the historic fabric of many major city stations in western Europe and in Asia. Particularly in Germany one objective of this rebuilding has been to create easy interchange between ground-level platforms and new metro line platforms below ground. Reconstructed German city stations are also unparalleled for their range of shopping, snack-bar, and restaurant facilities. Another reason for reconstruction has been special provision for new high-speed train services; examples are the Atocha, Nord, and Waterloo termini in Madrid, Paris, and London, respectively. The majority of stations built to serve city airports, generally from platforms beneath a main airport terminal, are on branches of a city’s commuter rail system. Those at Frankfurt (Germany), Schiphol (Netherlands), Gatwick (England), and Zurich and Geneva (Switzerland) are directly connected to their national railroad’s intercity passenger services.

Diesel and electric locomotives require few maintenance shops as compared with steam locomotives. Car shops, too, have been reduced in number and made more efficient through the use of process-line techniques. It is usually more efficient to construct new shop buildings rather than convert old ones to handle modern types of rolling stock.

Tunnels

Although very expensive, tunneling provides the most economical means for railroads to traverse mountainous terrain, to gain access to the heart of a crowded city, or, more recently in Japan and Europe, to project a railway across a maritime strait below its seabed. Railroad tunnels, however, confront the construction engineer with some unique problems, particularly in the ventilation of very long bores and in mastery of difficult geologic conditions.