A combination train and tram system is very good too. Trains service around the city and the tram or bus can run a logical local travel route. Busses are popular because they do not require track, but a tram can hold more and the stock can usually survive a longer time. They are also heavy and very difficult to tip. A bus and a tram are usually the same to electrify with the overhead cable. A bus can easily leave the route but a tram can transform into light rail for part of the route if separated. Both are built as low floor today, and should stop at a raised platform, but if this is not the case because of poor infrastructure, a bus can usually kneel and present the ramp to the ground level, but in these case the tram should always be selected to have a close gap or a ramp which can reach all platform in the system.