They are probably just a bad combination. What with a limited consumer market, road safety regulations, boat safety regs (no doubt), emissions standards. I assume that in addition there are many engineering problems which makes mass producing an amphibious car impractical. And they would probably have horrible, disastrous road manners, not to mention limited boating pleasure. Just buy a trailer.

>Steel bodywork rusts, and to prevent rust requires conscientious maintenance. After use in water the Amphicar required greasing at thirteen points including one that required the removal of the rear seat.

Freshwater rust is a non-issue compared to what they put on the road in the winter in some places.

That's from the article, which describes the vehicle used by Pres. Johnson. One could hope some progress have been made since then.

Seriously though, why?

What use is it other than novelty?

I mean if you live in Venice maybe?!

>> Venice maybe?!

Or Vancouver, Seattle, San Francisco, New York, London ... basically any city with a harbor and big bridges crossing it. The ability to bypass the line for the bridge and drive a relatively strait line across the harbor to your destination is very appealing. The concept of hundreds, thousands, of tiny commuter boats crisscrossing a busy harbor is not. TopGear staged a race across London, with Clarkson driving by boat. It looks like lots of fun, so long as you are the one rich guy with the fastest boat on the river.

San Francisco may have a harbor and bridges, but it's hard to drive right into the water. After 911 they added balusters to prevent vehicles from leaving the roads, so you would not be able to access the water near a bridge from a car. Just because you have water next to land does not mean you can actually drive off a road into the water. For that you need a boat ramp, and while there are a few (maybe 3-4) such ramps in San Francisco, you will find that using them is a lot less convenient than driving across a bridge and you will need to go far out of your way to do that.

It is about 9 times faster on land than on water, so unless the bridge was quite congested it would still likely be faster. If the bridge is so congested that it is faster than taking that car in the water, the roads after the bridge are probably also congested so all you gain is jumping ahead in the congestion.

The situations where the bridge is very slow but past the bridge is not are probably sufficiently rare that it is not worth the extra complexity of an amphibious car for most people.

It might be more interesting and attractive in places without bridges. Depending on the speed and frequency of a ferry service, it is possible that the car on water would be faster.

Ferries will usually travel faster (the Seattle car ferries are around 2.5 times as fast as the Amphicar, and the fast passenger ferries are about 5 times as fast), but the Amphicar could still win if you have to wait a long time between ferries.

For example, the car would take about 2 hours to go from Seattle to Bremerton via the water. The state ferry on the same route would take about an hour, but the ferries are almost 2.5 hours apart so it would take you from 1 hour to 3.5 hours by ferry depending on how your trip aligns with the ferry schedule. (The car could do it in 90 minutes if you went by land instead, but that route goes through Seattle and Tacoma, so you could hit a lot of traffic which could slow you down considerably).

A car that can fly would be cool to use anywhere, but amphibious vehicles require a boat ramp or a private beach/lake with direct road to water access, which dramatically reduces the usefulness of pulling James Bond-style stunts.

I live near Paris and there are many ramps to put a boat in the Seine. It would be absolutely extraordinary to cross Paris on the river and then come back home and park in the street. (Also, freshwater.)