– A multimillion-dollar lobbying push by FedEx Corp. and other freight carriers may be about to open U.S. highways to a new generation of bigger truck trailers even as watchdogs warn the price will be roadway carnage.

A $55.3 billion transportation spending bill unveiled last week blocks a variety of safety measures opposed by the industry, at a time when the rise in truck-related deaths has bucked a trend of overall improvement in highway safety.

The bill would also do away with plans to require trucking companies to carry higher insurance coverage and make it harder for regulators to reimpose more stringent rest requirements for drivers.

“Christmas came early for the trucking industry,” said Rep. Nita Lowey, D-N.Y.

The trucking industry is a formidable force in Washington, spending $9.85 million lobbying Congress last year, and making $7.96 million in contributions to political candidates, parties and action committees, according to the Center for Responsive Politics.

Lowey and others decried how the industry was able to insert sweeping policy changes into unrelated budget legislation. A provision in the appropriations bill that would allow two trailers of up to 33-feet to be hauled in tandem, up from the current 28-foot limit, is drawing the most concern.

The longer trucks will be harder for drivers to handle, said Jackie Gillan, president of Advocates for Highway and Auto Safety, a coalition of consumer-rights groups and insurance companies. She cited research showing double-trailer combinations have crash rates 15 percent higher than single-trailer rigs.

FedEx said a study commissioned by FedEx, Con-way Inc. and other shippers showed that the extra 5 feet in length would save gas and cut carbon emissions and would reduce the number of trucks on the road. “There’s no safety issue,” said Dave Osiecki, executive vice president with the American Trucking Associations. “There’s an environmental benefit and a fuel-economy benefit.”