Safety first: Although parapets and barriers along the Tuen Mun highway, and other locations, have been strengthened, it is up to drivers to obey laws to prevent accidents.

Bridge parapet and roadside barrier-enhancement works at locations an expert panel identified after a tragic bus crash more than two years ago have been completed, Highways Department Assistant Director for Development Ng Kam-chi says. He added  that, however strong and reliable highway parapets and barriers may be, their presence cannot prevent traffic accidents.

Speaking at a press briefing this afternoon, Mr Ng said the department had completed bridge parapet and roadside barrier-enhancement works at the 39 priority locations identified by the Tuen Mun Road Traffic Incident Independent Expert Panel.

That panel was set up after 21 people died and 20 others were injured when a double-decker bus crashed through a guardrail and down a hill off Tuen Mun Road near Ting Kau Bridge on July 10, 2003.

Mr Ng echoed the key point in the panel's report when he reiterated that road safety - first and foremost - requires drivers to drive safely and lawfully.

The department conducted full-scale impact tests and computer-simulation analysis on the enhanced designs of bridge parapets and roadside barriers for containing double-deck buses, he said.

Three roadworthy double-deck buses and a saloon car were shipped to a testing ground in Beijing for these tests and analysis.

"The full-scale impact tests provide useful data for onward formulation of sophisticated computer models to simulate various impact scenarios," Mr Ng explained.

"A real bus was dismantled and data were collected  to establish a realistic bus computer model. The computer-simulation models were calibrated against the impact tests and very good correlations were achieved. Using the calibrated computer models, more simulation runs were done to investigate impacts of buses and cars with different parapets and barriers at various impact angles, speeds, and vehicle loading conditions," Mr Ng said.

"The study confirmed the new designs to be effective."

The enhancements included:

* strengthening of existing three-rail metal parapets by adding intermediate posts and a top rail;

* strengthening existing concrete parapets by adding two strong rails and posts;

* providing three-beam barriers in front of parapets where space was available;

* replacing existing facilities with four-rail parapets; and

* upgrading existing roadside barriers to double three-beam barriers.