In the begginning there was the horse and kart. Then came along trains which were a much more agreeable alternative because of their ability to get you to your destination a lot faster than on a horse. But the motor car came along, which was considerably faster than the horse and cart, and even as fast as trains. As driving became a viable alternative to going by train in terms of journey time, more and more did. As a result railways have lost market share. Note: Although there has not been a decrease in the number of passenger kilometers by rail, road traffic has grown while rail traffic has remained static or grown very slowly.
High speed rail has changed that because it has enabled rail to win back some of the transport market. The question I wish to raise is, will history repeat itself? Is there a new fast car around the corner which will render high speed trains obsolete?
There is one thing for certain. Cars will always pollute the enviroment many more times than trains will per passenger. Some people say cars are getting more efficient, but trains are at the same time. It is quite simple, one large vehicle with one engine will be more efficient than lots of vehicles especially when the vehicle is as large as a car (relative to the size of the passenger).
In the UK there is a national speed limit of 70mph (112km/h). Typically across Europe speed limits tend to be in the order of 100-120km/h (60-75mph) for motorways. It is fair to say that if there were not such limits a lot of cars could probably reach speeds of up to 125mph (200km/h) perhaps even more. From a technical point of view the car is not that much slower to trains. It is only limited for reasons of saftey.
There is two key differences between road vehicles and trains. A road vehicles relies on a driver constantly giving guidance based on his/her own sensory input. A train runs along the tracks and is self guided. The second difference is signalling. As a rule two vehicles travelling in the same line in the same direction should always leave enough distance between them to come to a full stop from their running speed. Car drivers rely on their eyes for this. Trains have signals. Studies have shown that along a motorway the vast majority of drivers do not leave enough distance to come to a complete stop, which is why pile-ups occur. The braking distance increases with the square of the speed, ie if you double the speed you quadrouple the stopping distance required. This means that the faster the cars go the lower the capacity of the motorway. On busy days on the M25 in england a 50mph (80km/h) speed limit is introduced because it results in reduced jam-ups and delays because of increased capacity.
Thinking well ahead for the next 50 years perhaps the biggest threat to high speed trains will be computer controlled cars. A prototype was built in Germany in 1995. The idea is a computer drives the car by having about 15 sensors all the way round keeping track of the edge of the road, distance to next car etc. Because a computer can be programmed to be more responsive than a human high speeds would then be safe. If cars could do 125mph then high speed trains would loose a great deal of market share. But this would be a long way off. A motorway permitting these sorts of speeds would have to ban human-driven cars for saftey. Also the energy consumption of cars starts to increase dramatically after about 50mph (80km/h). This is because air resistance kicks in and the engine runs with fuel fully open. There is no way to get around that. High speed trains have the advantage in that they disturb a very small amount of air relatively. Imagine the cross sectional area of a eurostar, then imagine the cross sectional area of 800 cars - air resistance will be a lot greater with the cars. People might find that 5 miles to the gallon isn't a very efficient!
At the moment the the UK most rail services are mirrored by competing bus services. Buses take about twice the journey time as the trains but cost only half as much. Bus companies have a major advantage - infrastructure maintainance doesn't come into their operating costs since roads are provided by the government. If high speed buses were introduced that could cause a problem. Naturally high speed buses would have to be computer driven for saftey. Even so such buses would have problems competing with trains. The friction from rubber tires is always going to be more than from steel wheels. This is becuase as it goes round and round it is constantly deforming at the bottom and reforming, giving off heat. Steel wheels do not deform. All buses rely on diesel engines, with the exception of Trolley buses in London in the early 20th century which picked up electricity from overhead wires. Now diesel engines have a limited power output. It seems unlikely that a bus could be made to do more than about 100mph (160km/h) since diesel trains only do 125mph (200km/h). Wires could be stretched along the length of the road for electric buses, but when you talk about that type of thing you might as well build railways.
One thing is for certain though, in a world with a rapidly increasing population there may be too many people for everyone to have their own private transport, so perhaps this will not happen, especially with third world countries looking to develop their own systems.
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