Not just anybody can go out and run a railroad train; to do so legally requires that the locomotive engineer hold a valid certificate issued under uniform Federal laws that apply to all railroads. Should an engineer's road driving record be considered in granting him or her an engineer's certificate?  Under Federal rules, the individual's driving record is indeed considered: violations and suspensions for driving under the influence are considered, going back three years; but there are no hard-and-fast rules for applying driving infractions when granting the certificate. There is no requirement that locomotive engineers hold a motor vehicle license at all.   Last year, New Jersey went a step beyond the federal regulations, passing a law that prohibits engineers from running trains if their motor vehicle license is suspended, according to reporting by Larry Higgs for NJ Advance Media (and published in the Star-Ledger on January 10). Two railroad unions called foul, saying that the state law is in conflict with the federal rules, is a solution in search of a problem, and that it would not do anything to improve rail safety. The unions noted that federal rules require engineers with an substance abuse problem to undergo treatment and be deemed "not affected by an active (abuse) disorder;" those who do not comply have their certificates lifted. The unions filed suit in U.S. District Court in Trenton on January 9, seeking to overturn the state law.