New Department of Transportation rules aimed at preventing accidents involving oil-carrying trains are too weak, and won’t be implemented until too late, according to lawmakers and public interest groups keenly focused on the issue.

Calling it a “significant improvement over the current regulations,” Transportation Secretary Anthony Foxx publicly issued the rule on Friday. The edict will affect rail transporters of flammable fossil fuels, most of which currently originates from North Dakota and Montana, in the form of Bakken crude.

Noting, however, that most of the new regulations leave potential “bomb trains” on the tracks until 2020, Sen.. Maria Cantwell (D-Wash.) responded to the rule, commenting that “the new DOT rule is just like saying let the oil trains roll.”

Beginning as early as 2017, but in some cases not until 2020, bomb trains—high hazard flammable trains (HHFT)—will have to be reinforced, enhanced with electronic braking systems, and subject to new speed limits and route restrictions.

But according to Cantwell, the rule is “more of a status quo rule than the real safety changes needed to protect the public and first responders.” She said that it still lacks mechanisms to address explosive volatility of the cargo and doesn’t do enough to limit rail car punctures.

Echoing the concerns of her colleague about delayed implementation, Sen. Tammy Baldwin (D-Wis.) warned in a statement on Friday that “inadequate tank cars will be allowed to continue carrying volatile crude oil until 2020 and in some cases—indefinitely.”

The Washington-based public interest group Public Citizen also criticized the Department of Transportation, conceding that the rule is a “step forward,” while saying Foxx’s order “does not fully safeguard communities from the threat of oil train infernos.”

The group also raised concerns about keeping substandard trains on the rails for years to come, and endorsed legislation introduced by Sen. Cantwell that would immediately bar certain types of transport cars deemed unsafe. The group described Cantwell’s Crude-by-Rail Safety Act as “the apex of what a regulatory response to the threat of oil train disasters should be.”

Cantwell’s legislation, opposed by rail industry lobbying groups, has languished in the Senate Committee on Commerce, Science, and Transportation since March. Along with Sen. Baldwin, the bill has three other co-sponsors, Sens. Dianne Feinstein (D-Calif.), Patty Murray (D-Wash.), and Jeff Merkley (D-Ore.). A companion piece of legislation was introduced in the House by Rep. Jim McDermott (D-Wash.).

There have been four derailments this year alone in the US and Canada, though none have inflicted as much devastation as a 2013 derailment in Lac-Megantic, Quebec. The highly combustible accident leveled the town and killed 47 people—a grim reminder as to why the transports are often called “bomb trains.”

Last month, DOT implemented new rules requiring rail transporters to disclose details about cargo to first responders during an accident, and others limiting HHFTs to a speed no higher than 40 miles per hour in residential areas.

The rule finalized on Friday sets an additional, universal HHFT speed limit of 50 miles per hour, or 40 miles per hour for trains not yet retrofitted to meet the highest federal standards.