Mexico City, Mexico — The Mexican government announced Friday that it will tighten inspections and lower maximum allowed weights for freight trucks after recent protests over a string of deadly accidents involving double trailer trucks.

Independent truckers partially blocked highways leading into Mexico City to protest rules allowing extremely heavy and very long trucks, something they say displaces them from hauling jobs and pressures them to overload their own rigs.

Mexico currently allows trucks to drive on two-lane roads with loads of up to 80 metric tons and lengths exceeding 100 feet, compared to a United States limit of 80,000 pounds (40 tons) on interstate highways.

Overloading and the use of double trailers on secondary roads apparently played a role in two recent road crashes.

On April 13, a semi-truck pulling two trailers of grain allegedly lost its brakes while speeding along a highway west of Mexico City, then the rear trailer broke free and slammed into a bus carrying university students. Five students and a teacher were killed.

A week ago, a double trailer truck on a two-lane road in the Gulf coast state of Veracruz also lost its rear trailer, which slammed into a bus carrying farm workers, killing 43 people.

The Federal Communications and Transportation Department issued a statement on Friday, saying it is lowering maximum weights by 4.5 tons, and limiting double trailers to 15.5 mile runs on secondary roads. At present, double trailers are theoretically limited to wider, main highways, but a special permit has allowed them to complete journeys on back roads.

The department also said double trailers will all have to be inspected within two months and that drivers of these vehicles will have to carry proof of the weight of the freight they are carrying at all times.

The department also said it will increase its inspection force by 14 percent and increase its current numbers on weigh-in scales from 63 to 88.