The transport ministry uncovered safety violations in 66 of 165 chartered buses inspected after last month’s fatal crash in Karuizawa, Nagano Prefecture, officials said.
Because the inspections revealed more violations at smaller firms than at larger ones, the ministry is planning to review criteria for chartered bus operations.
Since Jan. 21, the ministry has carried out inspections at 28 locations nationwide.
The Jan. 15 bus accident on a Karuizawa mountain road left 15 people dead, including its two drivers.
Inspectors found that the proportion of buses in which violations were found, including not having detailed written route plans, topped 50 percent at firms with 20 or fewer buses.
ESP, the Tokyo-based operator of the crashed bus, had a fleet of 12. The ministry found 33 cases of violations by that company in its special inspection after the accident.
The proportion of violations stood at about 28 percent for member operators of the Nihon Bus Association and 77 percent for nonmembers.
The number of chartered bus operators in Japan surged after deregulation in 2000. Only 48 percent of them have joined the association, which keeps its members up to date on government notices. ESP was not a member.
The ministry is separately conducting intensive inspections of bus companies that have been punished in the past.
As there are only some 360 government inspectors, the ministry plans to ask private-sector organizations to aid in the checks.
A senior transport ministry official said that instead of simply imposing penalties for violations of regulations, these checks must instead focus on whether firms actually improve their safety practices.