A new super siren which helps drivers locate the whereabouts of speeding ambulances is being given a practice run at Croydon.

The siren, which has been fitted to one of the station's 24-hour accident and emergency ambulances, makes it easier for road users to identify the direction of the ambulance thanks to a combination of the traditional yelp of the modern siren and "white noise".

The new siren, which covers a broad frequency range, was developed with feedback from LAS staff and means only motorists in the path of the vehicle will hear it clearly.

Croydon is one of 12 A&E ambulances being fitted with the "localiser" siren as part of a three-month trial period that hopes to improve road safety around London's congested roads.

LAS accident investigation manager Bob Pearcey explained: "Other emergency services have trialled new sirens but this is the biggest trial of its kind."

Converted for the new archive on 30 June 2000.Some images and formatting may have been lost in the conversion.