How Intercity Railways Learned from Metros: Part 7

Variations on the Theme

Once the main line railways realised the value of the metro style operation, they began adopting it and adapting it to their own requirements. In North America they introduced push-pull operation using a locomotive and a 'cab car'. This was similar to the British system using a DVT.

Figure 15: An MP40PH-3C type diesel locomotive at the head of a bi-level commuter train operated by GO Transit in Toronto, Canada. The other end of the train has a cab car. This is the standard method of operation for many North American commuter operations. Photo: Piers Connor.

These trains were usually bi-level, i.e. built with two decks in the section of each car between the doorways, each accommodating passengers (Figure 15). They are common in both North America and mainland Europe but they aren't seen in the UK because the structure gauge is too small. 

Figure 16: A typical American bi-level cab car leading a train on the San Diego Coaster service. The cab car is simply a passenger car with a driver's cab at one end. The cab controls the locomotive at the rear of the train through a multi-core control line running through the intermediate cars.

Every Car Powered

Looking at multiple unit trains, many built today are designed with every car powered, particularly those built for long distance services. They have, in effect, reverted to Sprague's original multiple unit concept where every car had at least two motors. This was largely because then the motors were very small and didn't produce enough power to move more than the car they were fitted to. As motor power developed, motors became more powerful and unpowered trailer cars could be added. Nowadays, all-motor car trains are seen on both metros and main line operations while some have a mix of motor cars and trailers. 

For long distance routes in the UK, the 'Voyager' multiple unit diesel trains introduced 25 years ago had power units on every car. While this is acceptable for pure electric units, having a 750kW diesel engine throbbing under the passenger seats for long periods is noisome and tiring. The old British format of a separate diesel power car at each end of the train was better for passenger comfort. 

Bi-Mode Trains

It has become fashionable in the UK to deploy bi-mode trains. They are equipped for electric traction at 25kV AC operation but additionally carry a diesel engine on several cars to allow them to be operated over routes beyond the existing electrified sections. The British government prefers this solution rather than spending money on electrification. 

Figure 17:  A 5-car unit of British Class 802 bi-mode formation at Reading on the Great Western Railway route. Bi-mode trains became popular in Britain when the government decided to avoid the expense of electrification. Photo: garstangpost.t21.

Several fleets of long distance trains have been built in the UK as bi-modes. Considering just one route like that between London and Aberdeen, a distance of 400 miles, 300 miles of this is electrified. Thus, for 75% of the trip, the train is carrying useless diesel engines and fuel tanks. It would be an interesting exercise to determine just how much energy is wasted in this way during each trip and to set that against the life cost of electrification over 40 years. We should not forget to include maintenance costs in the assessment, especially since diesel trains are more expensive to maintain and are less reliable than pure electric trains.