Chris Medwell, an expert in heavy vehicle accident reconstruction at Bloomberg Consulting in Gulf Breeze, Fla., said investigators typically focus on several issues when examine air brakes following a crash, including wear to parts and an adjustment device that compensates for wear. Filters on air compressors that feed the system can clog, and hoses can leak, among other mechanical problems.
But human error can also be at issue.
As the name implies, air brakes use pressurized air for stopping power, rather than the hydraulic fluid used in car brakes. Heavy weight in a vehicle, combined with an inexperienced driver in rugged terrain, can have risks.
‘‘A lot of inexperienced drivers on long grade will pump the brakes. ... Descending mountain grades is a special skill,’’ Medwell said. ‘‘You don’t want to apply and release, and apply and release, to maintain a constant speed. That’s what taxes the system.’’
Associated Press writer Julie Watson in San Diego contributed to this report.