Why do some subway systems (e. g. Paris, Montreal, Mexico City) have rubber tires instead of steel wheels?

Question

Why do some subway systems (e. g. Paris, Montreal, Mexico City) have rubber tires instead of steel wheels?

In: 313

Answer 1

For Paris, its because this technology was developed by the local operator (RATP) in the fifties. They wanted to reduce noise (important for aerial lines) but also increase capacity. Because rubber tires have more grip than steel wheels, it allows subways to accelerate and decelerate much faster. It also allows more important slopes and reduces vibrations.

However, it consumes more electricity on longer routes, generates heat and comes with a non negligible upfront adaption cost and increased fixed costs. So its not always as competitive as steel wheels (that also improved over time).

Now for other cities? Some were built by the RATP (Mexico & Montreal). Others for the above reasons. There are many different technologies, variations, from systems to systems.