Even with relatively low cost diesel multiple unit trains there will be losses up to quite high levels of traffic. This is illustrated in the following table which also includes a comparison with a bus service:—
Margins of Revenue over Costs for Low Density Passenger Flows
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Traffic density DIESEL MULTIPLE UNIT TRAINS BUS SERVICE passenger miles per route mile Margin over movement cost per mile Margin over total Margin Margin over cost over per mile (C) total cost (A) cost (B) Hourly per mile Two-hourly per mile service service Per week Per annum Per annum Per annum Per annum Per annum £ 37 1,000 - 2,000 3,000 4,000 5,000 | | | | | 6,000 7,000 8,000 9,000 10,000 15,000 20,000 20 882 MM 88 17 +33 25 + 66 +100 £ £ £ £ £ 1,900 -3.700 -5,900 -1,000 300 - -1,500 -3,300 -5,500 600 + 100 - 1,000 -2,800 -5,000 200 + 600 600 -2,400 -4,600 + 300 400 -2.200 Y -4,400 + 700 -1,800 -4,000 - 1,400 -3.600 900 -3,100 500 -2,700 - 100 -2,300 - 600 +1,200 + 400 + 900 +1,300 +1,700 +-3,400 +5,200 +1,600° +3,400
- System cost attributable to passenger operation only charged assuming profitable freight absorbs the rest.
- Whole system cost charged assuming passenger traffic only on the route.
- This relates to a bus service receiving the same revenue as on rail, and bus operation at 2s. 6d. per mile.
These figures serve to show that the revenue earned from up to 6,000 passengers per week is unlikely to be sufficient to cover movement costs alone. This means that money would be saved by discontinuing such a service, even if the route continued to be maintained at its full level of cost for the sake of other traffic. In general, however, the presence of passenger traffic on even a single track branch line adds about £1,750 per mile per annum to the cost of maintaining and signalling the route, and of manning stations. Therefore, even where there is freight traffic capable of absorbing a share of the route cost, stopping passenger services cannot be regarded as paying their full cost below a passenger density of about 10,000. Where there is no other traffic, routes carrying up to 17,000 passengers per week may barely pay their way.
Although a high proportion of passenger services operate over lines of low total traffic density, there are also a considerable number of similar services operating over more densely loaded routes. In most cases, these services are just as unsound, financially, as those operating over branch lines. Below about 6,000 passenger miles per mile per week they do not pay for their own movement costs, even with short diesel multiple unit trains. Also, just as on branch lines, the presence of a stopping passenger service on a main line adds appreciably to the system cost, by complicating the signalling, and by necessitating the provision and manning of small stations. To be truly self-supporting, therefore,
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