Following the derailment that killed four commuters in New York City on Dec. 1, there are good reasons for reviewing the delays to the deployment of positive train control to our national rail system. There are also good reasons to refuse any rail operator further time extensions in implementing these safety upgrades. And then let's start discussing other safety weak points of the

rail system, such as grade crossings. They are an important part of the safety picture, too.

Metro-North Railroad, whose train derailed in New York City, had just awarded a contract to install positive train control (PTC), which might have prevented the accident and its four fatalities and many injuries. The transit agency and many others in the U.S. must comply with the federal Rail Safety Improvement Act of 2008. It requires, by December 2015, rail operators to install PTC systems to avoid collisions and high-speed derailments for intercity passenger and commuter rail. The Metropolitan Transportation Authority had wanted a time extension but that should be out of the question now.

U.S. transit agencies are still working out terms and deadlines for implementation. For example, Los Angeles commuter-rail operator Metrolink—which, in 2008, dealt with a derailment caused by a texting engineer that killed 25—succeeded in pushing back its early 2013 completion deadline to summer 2013. The extra time was needed because the work involves a network of software, signal updates and communications towers and must interoperate with similar systems in freight railroad networks.

FRA's final rules and amendments contained many compromises. That should have helped move matters along, but Congress appropriated only $50 million in rail technology grants, and the Obama administration didn't make the issue a priority. Then, the Association of American Railroads sued over the implementation deadline. FRA subsequently backtracked on other aspects of the implementation, and everything pushed full implementation further into the future. After all the delays, "this is not the time to talk about more time," one former FRA official said last February.

Nor is it the time to ignore other aspects of rail safety. From January to September of this year, 45 people died and 34 were injured as a result of crossing collisions, according to statistics from the FRA's Office of Safety Analysis. Although that is an improvement over past years, it is hardly satisfying or the end of the story. Pedestrians and cyclists need more protection via consistent signage and electronic warning systems, a recent University of Illinois study concluded. While vehicle collisions with trains have gone down, pedestrian and bicycle fatalities have remained consistent. The important work of improving safety in the vital rail system is just beginning.