TORONTO - Anyone planning to take a bus trip in Ontario or Quebec should be ready to make alternative arrangements.

Greyhound Canada has threatened to lock out about 500 drivers and maintenance workers if contract issues are not resolved by Thursday.

That could disrupt plans for thousands of summer travellers.

All bus service in Ontario and Quebec would be affected, except for trips from Toronto to Sudbury, Ottawa to Sudbury and all points west.

The employees' union has already voted down a final offer from the company over the issues of pension and driving hours.

The lockout would affect 320 drivers and some 170 maintenance and terminal employees.

The head of the union representing Greyhound operators in Ontario predicts widespread commuter hassles if the lockout actually happens.

Greyhound operators expect the company will lock out its drivers and use American operators on cross-border routes as of 12:01 a.m. Thursday.