Buses can run on steep grades, but light rail cars are limited to grades of 6%.
Rubber-tired vehicles such as buses have incrementally better traction on dry pavement, but significantly lower traction in wet, icy, or snowy conditions. Furthermore, electric light rail transit (LRT) railcars – including streetcars (trams) – are capable of negotiating much steeper grades than is commonly assumed and included in system designs.
In general, it advisable to minimize grades on any new transit system as much as possible. However, where necessary (to access critical sections of a city, to contain costs, or for other reasons), LRT can handle grades as steep as 12% (depending on vehicle design, motor power, and other technical capabilities).