I belive that you posted before that you want to take the train to Utah. I doubt that once you are on board anyone is gonig to come and ask you for ID but with the hightened security across the nation as it relates to Commercial and common carrier transportation I'd venture a guess that there may be some sort of ID check when tickets are purchased. the ID check may be cross referenced against a terrorist watch list but not sure if its cross checked against active warrants. I suppose it depends on what the warrant is for.
Understand this however; at some point, somewhere you will be apprehended. People with warrants have been apprehended when they did absolutly nothing wrong, If your in a car that gets rear eneded at a stop sign and the police arrive you could be taken into custody, Perhaps you drive stone cold sober through a DUI check point, who knows. Folks who run from warrants are always looking over their shoulder.
The best advice is to retain an attorney local to where the warrant was issued and deal with it.
This information does not create an attorney /client relationship and should not be use or relied upon to make any decision in your case. Only consultation with your own attorney can provide you with the advice you need for your case.