Freight railroads are largely prepared for the Dec. 31 deadline to introduce positive train control, the remote-controlled safety technology designed to stop train collisions and other accidents, but there are concerns about commuter railroads’ readiness.

Observers also describe the insurance markets for railroad risks as robust.

Major railroad lines are required to install PTC systems by year-end December 2018, with possible extensions to Dec. 31, 2020.

But in testimony before a U.S. House of Representatives subcommittee in February, Robert L. Sumwalt, chairman of the National Transportation Safety Board, said his agency “is gravely concerned that the majority of the nation’s railroads required to install PTC will not have fully operational PTC systems” by the year-end deadline. “For each day that goes by without PTC, we are at continued risk of another tragic accident,” he said.

Mr. Sumwalt pointed to accidents including the derailment of a passenger train on Dec. 18, 2017, in DuPont, Washington, that apparently failed to slow down as it traversed a curve, killing three passengers and injuring 82 passengers and crew members.

Jim Beardsley, Washington-based chairman of Marsh L.L.C.’s global rail practice, said the freight railroads most affected by the PTC mandate have “been working hard and they’re in pretty good shape” with regard to fulfilling the mandate by year-end. “Where we see some of the challenges are in the commuter realm,” because of either “late starts or challenges with capital funding and the like,” he said.

A March report issued by the U.S. Government Accountability Office said seven to 19 of the 29 commuter railroads may not complete required PTC milestones before the 2018 deadline or qualify for an extension.

Nikki Burgess, Seattle-based senior regulatory specialist with Labelmaster, a hazardous materials transporter unit of American Labelmark Co., said the often financially strapped commuter railroads generally operate on tracks owned by freight trains, and so the issue insofar as their PTC compliance is concerned involves training and installing equipment on their trains, rather than track work.

“I’m not a fan of the delays,” said former Federal Railroad Administration official George Gavalla, president of Norwich, Connecticut-based Triad Railroad Consulting L.L.C. The law requiring PTC was passed in 2008. “They’ve had seven years” to install the systems, and now may be given until the end of 2020, he said.

“The railroads are still slow-walking this,” said Fred Millar, an Arlington, Virginia-based independent transportation consultant.

The FRA is apparently understaffed, and the material its staff must review is “quite onerous, and the question is, do they have the resources to review these plans?” Mr. Beardsley said.

Risks faced by railroads include derailment or collisions, including the possible release of toxic chemicals by freight trains.

Mr. Beardsley said although the risks of a passenger railroad collision or derailment are “far, far higher” than a toxic gas spill, the latter is a “real scenario that could happen” and potentially kill hundreds of thousands of people if it occurs in a major city. He cited a 2005 accident in Graniteville, South Carolina, in which a train carrying highly toxic chlorine and hydroxide, a strong corrosive, collided with a stationary train, emitting a lethal gas cloud that killed nine people.

However, Bill Anderson, president of Rail Services Inc., a railroad safety and claims consultant in Boise, Idaho, said: “They’ve been transporting hazardous commodities for decades pretty darn safely. Once in a while, you have a big, spectacular, front-page grabbing accident, but compared to trucks, particularly, there’s fewer accidents.”

By the typical measures of safety, “railroads continue to become more safe with each year,” said Dan Bancroft, New York-based transportation practice leader for Willis Towers Watson P.L.C.

There is a $295 million-per-cap occurrence on railroads’ liability for accidents involving commuter trains, which does not apply to non-passengers or property damages. There are no tort caps on freight rail transportation.

David Adamczyk, New York-based executive vice president of U.S. railroad for Aspen Insurance, said positive train control’s implementation “could only be positive” in terms of insurance coverage. While “it’s not going to solve everything,” it “will go a long way towards resolving human error,” he said.

“I think the market is good for the industry right now,” Mr. Adamczyk said. “There’s plenty of capacity, both domestic and international,” but being 100% compliant with positive train control “can only help the railroads in terms of bringing costs of insurance down.” Mr. Bancroft said: “The market for passenger liability insurance is robust, with more than $2 billion of total capacity or limits available.

The strength of that market really comes” from the Lloyd’s of London marketplace, London-based insurers and the Bermuda market, which provides high excess capacity.