The mother of a 13-year- old boy who was killed in a school bus crash has welcomed the start of work to improve safety on the notorious road where he died.

Helen Ryan-Vig, of Barry Avenue, Bicester, is pleased safety signs have started to go up at the accident blackspot on the B4100 between Souldern and Aynho.

Her son, Blessed George Napier pupil Tomas Ryan-Vig, was killed on the road in May 2004 when his school bus was in collision with a tractor.

Northamptonshire County Council has now upgraded the road's danger status from flashing amber to red -- the highest possible level.

Category red means four or more people have been killed or seriously injured within a one kilometre stretch over three years, and allows casualty reduction work to begin.

Signs warning of the dangerous bend and recommending a speed limit of 40mph went up last week.

Two flashing vehicle-activated signs will also be installed, one on each approach, as well as new black and white chevron signs.

Although the speed limit will not be legally enforceable, drivers who ignore it could be charged with other offences such as dangerous driving.

Mrs Ryan-Vig said: "We have been campaigning since the accident for something to be done.

"As to whether it will be enough I have yet to find out -- because it will only be once they are in there that we will see how traffic reacts."

But she said the measures would not prevent all accidents and added she would have liked to have seen speed cameras or a one-way restriction.

She said: "It's on a tight bend so there is a very limited view. I am sure they could make it one way. That is the only thing that is going to prevent any more collisions at all.

"But given that there was nothing there at all, we hope it will make a difference."

The work, initially estimated at about £60,000, is costing £35,000.

A county council spokesman said: "This road is a priority for casualty reduction work, and the signs are the first part of a programme of measures.

"The impact of those will be carefully monitored as that programme is rolled out."

In the last three years, there have been four serious accidents on the same bend.

A woman was killed there just a few months after Tomas's death.

An inquest into Tomas's death recorded a verdict of accidental death in April this year.

Tractor driver Benjamin Andrews, 27, of Bethersden in Kent, has denied driving without due care and attention.

He is due to appear at Northampton Magistrates' Court in December.