TeeJay said:
According to the AA route planner driving from Brixton to Cardiff would be 153.9 miles and take 2hr 56min. Depending on the engine size and type this could cost about £20 in petrol (ie £40 return) although if you factored in the overall cost of owning and running a car at 40p/mile it would then be £120 return (as well as any parking costs and tolls).
Without wishing to appear like an unreconstructed petrol head

I don't like to see wooly thinking going unchallenged.
Presumably you're using the 40p per mile figure that's the Inland Revenue's claim allowance when submitting your tax return. However, this includes the cost of your fuel. In which case, you're counting the £40 on fuel twice. Correct that error and the cost of the journey is reduced to £80.
However, if one were to use the figures from the
AA Cost of Motoring Report 2005, with an annual mileage of 10,000 miles and a car costing between £10,000 and £20,000 when new, the total standing and running cost per mile (including depreciation, servicing, parking, tolls, etc. and fuel at £1.00 per litre) is 45.6p.
At that rate, the 307.8 mile return journey will cost £140.36.
With a small petrol car that costs below £10,000, at 36.48p per mile -> £112.29. N.B. The running cost component of that is 17.24p per mile.
Now that's not far off your figures, I'll agree, but arrived at on a much more sound basis.
For comparison, if one were to hire a small petrol car for two days (I've just got an online price) that would cost £77.97, with all fixed overheads included. With fuel at £31.06 (10.09p per mile as per AA figures allowing 98.1p per litre) the total cost of the journey is £109.03.
What this does highlight is that,
if there is more than one person travelling, the marginal cost of motoring is relatively low once one has paid the fixed overheads of owning a vehicle such as depreciation, insurance and Road Tax.
The marginal cost of the journey for someone who already has a small car would be £53.06 (17.24p x 307.8 miles).
In contrast, the rail fare of £135 is
entirely marginal cost. Choosing to travel by rail for this journey when one already owns a small car would present an opportunity cost of £81.94! Even in comparison with hiring a vehicle from a company that is spreading the fixed costs elsewhere it is less advantageous, but nearly £26.
I'll happily concede that I've ignored the Ed's point about the wider costs of using a car, though I might contend that they're perhaps not as great as he assumes when discouraging the use of cars for these reasons is one of the primary motives for the current levels of Fuel Duty and other charges by government.
Counterpoint
In situations where you are the only person making a journey, the train is a much more attractive option. £53.00 for the return fare, according to nationalrail.co.uk, which is apparently cheaper than using a car, albeit by only six pence.
The implications if we are to encourage people to use other modes of transport seem fairly clear if looked at in terms of economics.
- reduce fixed costs of motoring - e.g. scrap Road Tax
- increase marginal costs of motoring - e.g. higher Fuel Duty (which is the only approach already being taken by government)
- discounts for groups of people travelling by public transport
The Obvious Conclusion (TM): Single people without families will be more likely to use trains.
