> The trouble is, if you're in a motorway where every one of the now four lanes of traffic is going at the speed limit of 70 miles an hour (or, more likely, 80

> The trouble is, if you're in a motorway where every one of the now four lanes of traffic is going at the speed limit of 70 miles an hour (or, more likely, 80 miles an hour) and your tire explodes This actually happened to a family member of mine on the M1. Tire exploded and rolled straight off across the motorway. It took several minutes for the motorway operators and to close the lane that their car was stranded on. The driver and passengers had to get out of the car onto a live motorway lane just to reach the safety area behind the crash barrier. Thankfully everyone was OK, but it cemented my belief that smart motorways are an utterly, ridiculously and unquestionably stupid idea.