Data shows that M4 Bus Lane speeds up travel times

The M4 Bus Lane opened on 7 June 1999 to a chorus of disapproval from groups representing motorists. But data from the TRL has proved the critics wrong. Comparing traffic on the 3.5km stretch before and after the bus lane opened, all types of traffic have experienced decreases in journey times – despite a 10% increase in traffic in the months after the bus lane became operational.

During morning rush hour, the following journey time decreases have been noted:

• coaches and taxis using the dedicated lane save up to 9 minutes
• other vehicles save up to 6 minutes

An average of 3,400 vehicles use the bus lane daily: 700 are coaches or minibuses and 2,700 are taxis.

Improved journey times were also documented during the evening rush hour and on Sunday evenings.

But outside rush hours, journey times increased by 1 minute for buses and 30 seconds for other vehicles. This was due to new speed limits.

TRL’s study was conducted on behalf of the Highways Agency. Data from the first three months of the bus lane’s operation showed that there is no evidence that motorists are leaving the M4 early and diverting to smaller roads. It also found that traffic is running more smoothly with the bus lane in place, with an end to the bottleneck that used to exist where the M4 narrowed from three to two lanes just before its elevated section into London.