Proposed federal safety standards for high-speed rail in the United States likely will not affect development of Japanese rail technology in Texas, but if approved all but assure those trains never share tracks.

The regulations, released earlier this week and subject to final approval by the Federal Railroad Administration after 60 days, would set safety standards for passenger trains traveling more than 150 mph. Current rules set strict standards for trains traveling at slower speeds.

“As several regions of the United States build faster passenger rail service, the trains on those tracks must keep passengers safe,” said U.S. Transportation Secretary Anthony Foxx, in a news release. “To do that, we want to allow manufacturers to innovate and achieve all-new levels of safety. These proposed changes put us on track to do just that.”

Among the planned high-speed rail projects is a Houston to Dallas route planned by Texas Central Railway. The company, with private financing, plans to use Japanese trains capable of making the trip between the two metro areas in 90 minutes capable of reaching a top speed of 220 mph.

American and Japanese safety standards differ. While American trains – and many European train systems – mix freight and passenger traffic, Japanese trains are designed to minimize damage in collisions and protect passengers with cars built to absorb the energy of the crash.

Japanese train systems are built to control braking and monitor the trains.

“The key to the Japanese high-speed rail network’s ongoing safety and reliability is the ‘principle of crash avoidance,’” U.S. regulators said in the proposed rules. “Unlike the typical operating environment in the U.S., no conventional train service runs on the Japanese system and it has full grade separation.”

No passenger on a Shinkansen train -- the model Texas Central would use -- has ever died as a result of a crash, after more than 50 years of operation and 5.5 billion passenger trips. Fatalities outside the train are exceedingly rare, with only one reported occurrence in 2013.

Based on the proposed federal rules, a Japanese system will almost certainly never mingle with existing rail traffic.

“Although FRA believes that the proposed … requirements would allow Japanese trainsets to be modified for use in the U.S. market and be inter-operable, it is also expected that those required modifications would be costly,” regulators said.

Modifications to Japanese trains to make them meet the proposed standards would be about $4.7 million per vehicle, according to regulators.

The safety standards, if approved, mean Texas Central could still operate if federal authorities allow it, but its use would be restricted to its own track that’s entirely separated from all roads and rail lines. In a statement, company officials said that has been the plan all along.

“The new regulations being discussed do not limit the ability to coordinate with transportation organizations to ensure passengers seamlessly get to their final destination, which we are committed to,” Texas Central officials said in a statement.

In Houston, the lack of sharing tracks makes station location crucial, and extending further into Houston’s core complex and costly. Texas Central plans to stop near Loop 610 and U.S. 290, north of Uptown.

Local officials are already weighing plans for how to connect downtown-bound travelers to the central business district, which could mean additional local investment in light rail, or possibly commuter rail.

Texas Central said specifics of those options are "premature" as they continue their process with federal rail authorities.