For connections to smaller destinations south of the border, there are numerous domestic Mexican bus companies.
If you're driving into the USA from Mexico, bring the vehicle's registration papers, proof of liability insurance and your driver's license from your home country. Mexican driver's licenses are valid, but it's worth having an International Driving Permit (IDP).
Very few car-rental companies will let you take a car from the US into Mexico. US auto insurance is not valid in Mexico, so even a short trip into Mexico's border region requires you to buy Mexican car insurance, available for around $25 per day at most border crossings, as well as from AAA (www.aaa.com).
For a longer driving trip into Mexico (25km or more beyond the border), you'll need a Mexican permiso de importación temporal de vehículos (temporary vehicle import permit), available at the border for $60 or online from Banjercito (www.banjercito.com.mx/registroVehiculos) for $53.
Greyhound has direct connections between main cities in Canada and the northern USA, but you may have to transfer to a different bus at the border. Book through Greyhound USA (www.greyhound.com) or Greyhound Canada (www.greyhound.ca).
If you're driving into the USA from Canada, bring the vehicle's registration papers, proof of liability insurance and your home driver's license. Canadian driver's licenses and auto insurance are typically valid in the USA, and vice versa.
If your papers are in order, taking your own car across the US–Canadian border is usually fast and easy, but occasionally the authorities of either country decide to search a car thoroughly. On weekends and holidays, especially in summer, traffic at the main border crossings can be heavy and waits long.
Amtrak (www.amtrak.com) and VIA Rail Canada (www.viarail.ca) operate daily services between Montreal and New York, Toronto and New York (via Niagara Falls), and Vancouver and Seattle. Customs inspections occur at the border.
The USA has more than 100 official border crossings with Canada in the north and almost 50 with Mexico in the south. It is relatively easy crossing from the USA into either country; it's crossing into the USA that can pose problems if you haven't brought all your documents. Some borders are open 24 hours, but most are not.
Busy entry points with Canada include those between Detroit, MI and Windsor, ON; Buffalo, NY and Niagara Falls, ON; and Blaine, WA and Douglas, BC.
The main USA–Mexico border crossings are between San Diego, CA and Tijuana; Nogales, AZ and Nogales, Sonora; El Paso, TX and Ciudad Juárez; and Brownsville, TX and Matamoros. As always, have your papers in order, be polite and don't make jokes or casual conversation with US border officials.
Cartel violence and crime still pose risks along the US–Mexico border. Before heading out, check the latest warnings from the US State Department (travel.state.gov).