Dr Mawhinney's predecessor, John MacGregor, had a disturbing enthusiasm for all things on four wheels. He proposed that motorists should to be charged electronically as they passed a toll point and that the money raised should be spent on new roads.
On a superficial level this seemed to be a neat way to improve the transport system while also reducing traffic congestion, without imposing extra costs on taxpayers. But there was, as Dr Mawhinney has now tacitly acknowledged, just one problem: the policy would not work. First, tolls on only a few major roads and motorways would encourage motorists to divert to alternative free routes. Second, protests such as those against the M11 link road demonstrate that spreading miles of fresh tarmac across the shires has become politically impossible.
Yet Dr Mawhinney should not now give up on road pricing. If he can think bigger and more imaginatively than Mr MacGregor did he could begin to develop a serious response to congestion, pollution and millions of hours of wasted time.
For road pricing to work it must apply to most of the trunk network and to urban areas. A comprehensive policy would prevent drivers from switching to free alternatives, would reduce the flow of traffic into cities and might also help everyone to breathe more easily.
But the most important switch that Dr Mawhinney must engineer from his predecessor's policy is in the way that the revenue would be spent. New roads are off the agenda. Likewise, if it needs saying, the option of the Treasury pocketing the proceeds can be ruled out on the grounds of unpopularity.
Instead Dr Mawhinney will have to overcome Conservative distaste for public transport (as articulated by Steven Norris, the Transport Minister) and spend the takings on buses, trains and light rail systems. Expenditure in these areas would give those priced off the roads a real alternative way of reaching their destination. Without such developments, road pricing would provoke such hostility that no party seeking election could sensibly support it.
Dr Mawhinney has in a number of recent speeches made clear his wish for a proper debate on the British transport system. Scrapping Mr MacGregor's ill-fated proposals is a good first step. But does he have the courage to take the next step and acknowledge that a century of free road transport must now be brought to an end?