But reserving the route to specially-equipped buses would ensure that only a small fraction of the capacity of the rail right-of-way would be utilized. Only twenty buses per lane per hour are expected to use the system in peak-time in 2016 – taking up less than five per cent of lane capacity! Cambridgeshire expects to receive some £70 million of taxpayer’s money to implement this sadly inefficient project. Could it do better?

One answer can be found in the US, where some motorway lanes are reserved for “High-Occupancy Vehicles” (HOVs) such as buses and car-pools. But HOV lane capacity is wasted when there are not enough HOVs to utilize it.

The problem was successfully solved in 1995, on State Route 91 in California, by allowing the spare HOV-lane capacity to be used by toll-paying vehicles, the tolls being collected electronically, without vehicles having to stop. The tolls vary with traffic, and are kept high enough to ensure free flow at all times. Those lanes (dubbed “HOT Lanes” because they can be accessed by High-Occupancy or Tolls) are being considered for other US cities because they have the following advantages:

* They assure congestion-free travel on payment of a fee; * They provide congestion-free facilities to designated HOVs, at no charge; * They reduce congestion in other lanes by drawing away some users; * They expand road capacity without expanding infrastructure; * They raise revenues, possibly enough to be self-financing.

Might there be an opportunity now in Cambridgeshire to improve on the “guided busway” concept by re-configuring it as a “HOT Lane”? There would be the additional advantage that the tolls might make such lanes attractive to private finance. It would, in essence, allow road users to buy their way out of congestion, while providing a toll-free facility for public transport. All this at little or no cost to public funds, which could be reserved for projects more difficult to finance privately, such as pedestrian or cycle facilities.

There are not too many projects which offer clear benefits at no obvious cost. Are not HOT lanes on disused Cambridgeshire railways worth exploring further?