users want to see a 'zero tolerance' approach towards vehicles disobeying a red X. Effectiveness Reduced relative cost In 2007 it was estimated that ATM could be introduced within two years at a cost of around £5-15 million per mile as opposed to 10 years and £79 million per mile for widening. In Autumn 2018, alteration of the M4 between junctions 3 and 12 was commenced, a length of 32 miles (51 km). Construction was completed in March 2022, but as of July 2022 calibration work of some sections is still underway. The cost was £848 million, representing £26.5 million per mile (£16.6 million per km). Emergency stopping areas in this section of the M4 have been provided every 1.3 miles (2.1km). Initial experiments The M42 scheme was initially run as an experiment and a Highways Agency report into the first six months of the scheme showed a reduction in variability of journey times of up to 27%. The journey time statistics can be broken down to show that northbound journey times were reduced by 26%, equating to an average reduction of 4 minutes as compared to the period when the variable speed limits were on, but the hard shoulder was not being used, and 9% southbound (equating to 1 minute) during the afternoon rush hour. The report also indicated a fall in the number of accidents from over 5 a month to 1.5 per month on average. The Agency did state that normally accident statistics should be compared over a 3-year period, so the initial results should be treated with caution. They also stated that no accidents had been caused by hard shoulder use as a normal lane. The report also stated that there had been a 10% fall in pollution and 4% fall in fuel consumption. The report also indicated a compliance rate of 98% to the indicated speed limits when using the hard shoulder. For comparison, before the introduction of mandatory speed limits at road works, the compliance rate was 10% as opposed to 89% afterwards, showing a similar effect. Road capacity All lane running motorway upgrades improve journey capacity. The Government argues that this improves safety as it encourages drivers away from statistically more dangerous rural or A roads. A smart motorway can carry 1,600 additional vehicles per hour in each direction, and up to 11,000 journeys a day. In the short term, smart motorway upgrades