All the Washington State ferries allow you to stay in your car. Being in a front car in bad weather can be interesting. All the car decks are open end to end, and the boats are double ended.
The ferries in our region are free, including the tourist attraction, the Kootenay Lake Ferry, which is the longest free ferry in the world. It's a 35-minute journey covering 8km, and operates year round.
Generally speaking the ferry is usually slightly cheaper, but whichever option you choose, make sure to shop around for deals and book well ahead of time to get the best-value fares.
The cheapest crossing is the ferry from Dover to Calais. Depending on how busy it is, DFDS or P&O is the cheapest option. What is the shortest crossing to France from the UK? The shortest crossing is between Dover and Calais.