Track Geometry for Light Rail Systems

Light rail systems are characterized by running over the streets, with semiexclusive (or reserved) right-of-way. This factor leads to the necessity of adapting the track geometry to that existing in the streets. This adaptation sometimes leads to great challenges: strong vertical grades, horizontal circular curves with small radius without superelevation, transition curves, vertical curves with small minimum radius, and so forth. Nevertheless, there are several good reasons for limiting track geometry parameters as far as possible, because of their influence in vehicle design, in the effects that the vehicle will have on the track (and on maintenance work), and in operational and construction costs of light rail systems. The limitations for different track geometry parameters were analyzed by comparing recommended maximum and minimum values of each parameter established by the Transportation Research Board and the International Union of Public Transport and by explaining interesting cases, which sometimes fall outside these parameters. The main reasons for each limitation, related to vehicle design passenger comfort or any other physical condition, are examined. Finally, the first conclusions of developing research on track geometry parameters and construction costs of light rail systems in Spain are presented.