A father last night welcomed a drop in the number of motorists injured on Oxford's Eastern Bypass - three years after the crash that killed his son.

The number of motorists injured has dropped in the 12 months since mobile speed cameras were first used to enforce a 50mph speed limit.

Thames Valley Safer Roads Partnership has noted a 32 per cent reduction in collisions and a 40 per cent reduction in injuries between May 2007 and March 2008, compared to the previous year.

Today is the third anniversary of the crash which killed schoolboys Marshall Haynes, Liam Hastings and Josh Bartlett, all 13, and 21-year-old Oxford Brookes University student Howard Hillsdon.

Although speed was not a factor in the crash, Marshall's father Dwaine Haynes, of Starwort Path, Blackbird Leys, said: "Anything that will make a reduction in the number on that stretch of road is welcome. The ideal scenario for me would be a permanent camera there."

Dan Campsall, a spokesman for the safer roads partnership, said: "It is a big change.

"While we can be pleased with the results so far, there is still a great deal of work to do, both here and elsewhere, to stop lives being wasted on the roads.

"Only one of the collisions since cameras were introduced on the bypass was caused by someone exceeding the speed limit. When drivers slow down, the roads become safer for all of us."

Mr Campsall said the stretch was monitored by mobile speed cameras at least once a month, but would not reveal how many motorists had been caught speeding over the past year.

Oxford resident Keith Brooks, who survived a crash on the bypass in 2001, welcomed the reduction in injuries.

But the 61-year-old, from Horspath, said putting crash barriers along the whole stretch was more important in reducing injuries than enforcing the speed limit.

The former digger driver, who was left with a broken arm and injured wrist, said: "Where I had my accident, between Horspath Driftway and Horspath Road, there are still no crash barriers."

The total number of collisions dropped from 19 in 2006, to 13 in an 11-month period between May 2007 and March 2008, while the total number of casualties was cut from 25 to 15 in the same period.

There were 16 collisions in 2005 and 21 collisions in 2004 on the same stretch, resulting in 42 and 28 casualties respectively.

In October, an Oxford Mail speed check showed almost one car a minute was speeding.

Although speed was not a factor in the 2005 crash, the limit was cut to 50mph and a barrier installed.