I cross it every day as part of my commute to work. It's no big deal. There are no visa requirements for either Canadians or Americans, but you will need to have photo ID, like a driver's license. Your passport or your birth certificate is probably a good idea, too. The customs officials will ask you what nationality you are and normally ask to see your ID. Usually, they will also ask where you are going and if you are importing anything into the country.
However, since you are asking about access points with no customs/border patrols, maybe you have something to hide. If you
do show up at a border crossing acting nervous, that's a sure-fire way to get your car ripped apart.
