WHAT goes up must come down is a useful rule - until applied to the Stonebow bollard in York.

This hi-tech traffic measure makes a habit of going wrong. Sometimes it is shy and won't come out of its hole and at other times it stands proud and refuses to budge.

Then there are those days when it emerges from hiding just as an unfortunate vehicle is passing above.

This bollard is said to be intelligent and it certainly seems to have a mischievous mind all of its own, being quite willing to wreak havoc on a whim.

Buses, taxis, cars and ambulances have all been dealt a swift and low blow when the retractable obstruction has got its timing wrong. A properly synchronised bollard should help the traffic flow, but this one seems to go wilfully its own way.

Perhaps it becomes bored with going in and out at the right moment and prefers instead to have a little malicious fun.

Whatever the explanation, the bollard was at it again yesterday, declining to budge just as a number six bus was passing through Stonebow. Thankfully it seems that no one was hurt in this latest incident, although the usual chaos did ensue while the damaged bus was removed.

This bollard was installed in October 2000 by City of York Council to prevent "rat-running" through the city centre. It cost £60,000 - a figure which does not include the cost of all the damage it has done since.

The bollard remains a sound idea in theory, but it needs to be taught a better sense of timing.

Updated: 10:27 Friday, May 13, 2005