He smashed into it at 25mph in a cacophony of broken glass and tearing metal. The bus caved in, but the bridge didn't.
The demonstration had been staged by Railtrack to illustrated the dangers posed by the increasing number of high vehicles "bashing" into its bridges.
The bridge, in Whitehouse Road, Swindon, had the unenviable record of being the most bashed bridge in Britain with 82 hits since January 1990.
The 83rd seemed to be an attempt to turn the double decker into a single one. Even though we had been expecting the bang, it was a profound shock.
More than half the roof of the bus was removed but the bridge, which carries the Great Western main line, was undamaged apart from the sign reading "3.1m, 10.0" which was soon replaced. The bridge, built in 1910, was quickly passed as safe for the trains.
It is not always so easy. Since British Rail started monitoring strikes to bridges in 1990, the number has gone up from 806 to 1,101 last year, 59 per cent due to driver error and a third as a consequence of poor loading of the vehicle.
Newly-privatised Railtrack, which is now responsible, reckons such strikes cost pounds 5m in repairs and much more in train delays for which it now has to reimburse train operators.
Each time a bridge is hit, an engineer has to check it before trains can use it again, a process which often takes several hours since few people are qualified for the task.
Mr Carr is the man who risked life and limb in the Milk Tray advertisements to ensure that the lady got her chocolates. He emerged from the bus looking slightly shaken.
"As the glass shattered, it was so beautiful, it looked like a rainbow," he said. So that's why those thousand or more drivers a year do it. Britain's most damaged bridges January 1990-June 1996
1. Whitehouse Road, Swindon - 82 strikes
2. Stuntney Road (A142), Ely - 61
3. Mill Lane, Bradford - 54
4. Stoke Road (A5006), Stoke-on-Trent - 47
5. West Street, Glasgow - 43
6. Barrowby Road (A52), Grantham - 42
7. Hawkeridge Road, Westbury, nr Bath - 41
8. Station Road (B470), Langley, nr Slough - 39
9. Tregoss Moor Road (A30), Roche, nr Bodmin - 37
10. Dingley Road (A427), Market Harborough - 36Reuse content