M1 Widening Made Traffic Move More Slowly

Five years after the M1 was widened between junctions 10 and 13, traffic moved more slowly than before.

A study by Dr David Metz shows that this is due to digital navigation, or satnavs, diverting local traffic onto the expanded motorway, leading to more congestion.

The introduction explains that there is a general belief that investing in additional road capacity generates economic benefits.

‘The main economic benefit is supposed to be the saving of travel time…[but there is] a substantial discrepancy between forecast and outturn in relation to the widening of a section of the M1 motorway…The findings suggest a general phenomenon whereby the economic benefits to longer distance business users anticipated from road widening are negated by the use made of the increased capacity by local road users for short trips of less economic value.

There is reason to suppose that diversion of local journeys to the motorway to save time is facilitated by the widespread adoption of Digital Navigation (generally known as ‘satnav’)’.

introduction to the paper

The widened section of M1 opened in December 2012, and at the time substantial benefits to business users were forecast.

The traffic modelling turned out to be inaccurate, and the predicted economic benefits did not materialise.

‘There is therefore a good case to treat the strategic road network as mature, focussing on improving operational efficiency and exploiting vehicle-to-infrastructure connectivity in the form of Digital Navigation.’

abstract from the paper