But road owners would also face a series of trade-offs when setting speed limits. Under busy conditions, high speeds can reduce capacity, which in turn would reduce toll revenues. And in some locations, high speeds could increase the risk of accidents, potentially damaging the reputation of operators and reducing revenues through delays and higher insurance costs.
To a large extent, trade-offs between speed and other considerations would be time and place specific, depending on the nature of the infrastructure and its usage patterns. Moreover, since the decisions would be commercial, they would be beyond the scope of politics and the undue influence of special interest groups.
In this context, it is inconceivable that private road operators would set speed limits that not only increased journey times and lowered productivity but also worsened congestion and raised significantly the risk of serious accidents. Yet such controls are imposed by the government with its centralised approach to speed on state-owned roads.
Perhaps the most egregious example is the national 40mph limit imposed on heavy goods vehicles on single carriageway routes. This imposes substantial delays and productivity losses on the road haulage sector. And since roads carry around 70 per cent of freight within the UK, this has a significant impact on the wider economy. Worse still, slow-moving trucks create long tailbacks of other road users, for whom the national limit on such roads is 60mph. Delayed and frustrated, car drivers and motorists frequently engage in dangerous overtaking manoeuvres – the cause of a high proportion of fatalities and serious injuries on the network.
The government is currently considering raising the lorry limit on single carriageways to either 45mph or 50mph, but the move is opposed by various special interests. If roads are to remain outside the market economy for the foreseeable future, then transport policymakers should at least adopt a more commercial approach to managing the network. This means raising speed limits where it benefits users and basing policy on a rational consideration of the economic trade-offs rather than the demands of lobby groups.