I was at a meeting of the Transport Statistics Users Group in London yesterday.

Two people from the Association of Train Operating Companies (ATOC) made a presentation on their recent report on Missing Links - towns and settlements which were not rail connected but potentially could be.

The first speaker commented that, when stations and lines had re-opened since the 1980s, the results had tended to exceed forecasts - actual patronage was better than had been thought.

The presentation of the analysis of Missing Links showed that about 15 of these had a positive benefit:cost ratio. Detailed figures for one of them - Guildford to Cranleigh - were given.

In the discussion session afterwards, I said that, if the Treasury were to look at their figures, they would apply a hefty discount for optimism bias. Their argument would be that project sponsors are always too optimistic, so all cost estimates need to be increased and revenue estimates decreased to discount for this.

However, this was contradicted by the fact that re-opened lines and stations have exceeded forecasts - so is there still a case for this optimism bias? And if there is not, it needs to be an organisation with a nationwide view (like ATOC, Network Rail or a local authority association) which says so. I urged ATOC to make a start!

This led to an interesting if light hearted discussion about terminology - should we start talking about negative optimism bias?

Remember - you read it here first!

This potentially confusing piece of description reminded me of some other terminological infelicities I'd come across in the past.

In the 1970s, British Railways received grants for the socially necessary but unremunerative passenger sevices they were obliged to run. In some parts of the country - the deep rural areas and the commuter belt south of London - most trains were part of an unremunerative service. The odd ones which were not tended to be referred to as Non-Unremunerative Passenger Services!

I thought this was bad enough, but then came across a list of highway classifications. At that time, we had a category of road which was known as Non-Principal Unclassified !

No doubt there are numerous other examples of the mangling of the English language!