Greyhound is beefing up security on its buses in a massive overhaul that includes all major terminals in Canada.

Passengers now have to go through magnetic screening, and all sizable pieces of luggage must be stowed underneath the bus. Items carried onto the bus will be subject to hands-on searches.

The company says the changes -- which come in the wake of two violent attacks on Greyhound buses this year -- are the result of a two-year security study. 

In the summer, a sleeping passenger was beheaded by his seatmate. Nearly two months later, a passenger in northern Ontario was stabbed.

The new procedures were first implemented in western Canada, with Monday's expansion bringing them to most large locations in the country.