A TRAFFIC management scheme dogged by hitches in the past successfully passed a trial - only to fail another test five days later.

It is the latest hiccup for the Angel Street bollards, which failed to lower as they were designed to in order to let buses through.

Worcester City Council launched the scheme in January 2000 but it has never been operational. In July, the council said a fault in the electrical supply was to blame for the problems.

Aquila Networks has since carried out work on the substation in Sansome Walk.

"The power supply is now perfect," said Tom Comerford, senior engineer at Worcester City Council.

"We did a half-hour trial last week which was perfect. Then we did another a few days later and it went haywire.

"It's a bit of a mystery. It's gone pear-shaped again."

He said that since there were no problems with the power supply, the fault must lie with the area surrounding the bollards at the access to Angel Street.

"We've discovered we're not the only ones having problems," said Mr Comerford.

"It may well be that we've got issues like mobile phones and electrical equipment in nearby restaurants and businesses - anywhere that uses high-draining electrical devices.

"While the power supply has been proved to be as good as it can be, it doesn't take into account the external interference.

"We thought we had it cracked, but we're back to square one."

The city council had hoped to turn the bollards on full-time from Friday, November 1, but the latest hitch means traffic bosses have had to go back to the drawing board.

They could be forced to rethink the method used to lower the bollards, using number plate recognition instead of the transponder unit.