What is the minimum safe speed for a highway capable EV?

"Highway" is a pretty subjective term, now isn't it? If you meant FREEWAY, the top speed varies by 20mph that I know of from state to state. Around LA there are still 55mph limits, but Arizona and New Mexico get to 75mph.

Meanwhile, I think of a highway as being nonfreeway. Imperial Highway near my home is 45mph for most of it, but there is a section that gets up to 55mph.

I'll say I like the idea that it should get up over the speed limit for the road it is on. Although I can see where the sort of backwoods highways around my relatives in Texas that probably wouldn't be necessary.

In California a gas bike is required to be at least 150cc, theoretically 9hp, to ride on the freeway. Since 9hp for an electric would be 6,714 watts, do you require it? Or do you say a 9hp electric outperforms a 9hp gas engine and set the wattage lower? How fast can a 150cc bike really go?

There's no simple answer to this.

In my neck of the woods, the Interstates have speed limits that go from 55mph in town to 70mph between cities, but traffic in both regions tries to stay at 70mph all the time. I've ridden those highways on a 250cc Honda Reflex, with a top speed of about 75mph, and was generally able to keep up with traffic safely. However, the Reflex had no reserve speed left, it was going flat out as fast as it could, and was just keeping up. If I needed to get out of the way, or to pass a truck, going faster wasn't an option. Therefore, my personal take is that that bike needed about 10mph more in order to be a reasonable highway traveler. Since a 250cc bike wasn't quite enough, I went looking for bikes at 400cc or larger. (Ended up with a Honda Silverwing at 600cc).

So, based on that experience, I'm a pretty solid vote for 80+mph burst/passing speed, and 70mph sustained. 62mph just isn't fast enough, at least not given traffic speeds around here.

A car might be able to get away with a lower top speed than a motorcycle. There's less of a safety issue in a car, so reserve speed could possibly be sacrificed. However, I'd still be reluctant to take a car on the highway with less than a 70mph limit. And I might be willing to take a 70mph bike on the highway for short hops (a few exits), depending on traffic conditions at the time, but wouldn't do it regularly.

These numbers could change if traffic slows down on average, and I think it has slowed slightly over the last few years.

But I remind you, that IS how the argument will go.

And as the terms cause problesm with their meanings, so do the individual needs. It would take awhile, but I wouldn't be greatly afraid of the trip from say Canyon Lake to Fredricksburg in Texas on a 35mph bike. I wouldn't want to get near the major roads into San Antonio with one of those, but there's backroads.

In California I could get from Orange County to say Chino riding through Carbon Canyon with a bike at or under 50mph, and maybe some of the roundabout surface streets would work, but forget the freeway at that speed.

"Highway" is a pretty subjective term, now isn't it? If you meant FREEWAY, the top speed varies by 20mph that I know of from state to state. Around LA there are still 55mph limits, but Arizona and New Mexico get to 75mph.

Oh, that semantic problem. I didn't hear the word 'Freeway' until moving to California and back in the midwest it was "Highway" for the limited access 65+ miles/hr roads and "country road" for the two lane roads that might have had a slower speed limit. I really have no idea how universal the word "Freeway" is - and it's not worth debating the word "Freeway" or "highway". What I meant is the 65 miles/hr speed limit limited access roads. The roads you called "Freeway".

David - I believe the common federal term for what you're speaking of is "restricted access highway". There's a sign on the on-ramp describing what's not allowed to use it.

However, like Mike, my rule of thumb is I want a vehicle with 5 to 10 mph more than the posted limit to feel comfortable. If I just have to do a short distance (say one hop down a freeway/highway/restricted access thing) I'd compromise that comfort zone. However, for a commute on the I-94 (my local freeway) I'd want an 80mph capable bike and I'd ride it at 70mph (the posted limit).

I think the commentator you mentioned is incorrect in creating a blanket statement. It's all about intended usage.

Haven ridden/driven cars, motorcycles and scooters on various highways/freeways, I can sasy the I feel that for use in the USA, a vehicle should be able to sustain 60-65 mh, both uphill or over level ground, with or without a headwind of as much as 30 mph, and speeds of 75 to 80 mph should be attainable for up to 30 second bursts, to enable getting out of the way, lane changes, and passing! --I do NOT feel that my VECTRIX really has adequate margin for safe operation on the highway, with its present 62 mph limit. I could really appreciate a vehicle that goes zero to 60 mph in 10 seconds or less, cruises effortlessly at 60 to 65 mph,and could attain 80 mph for up to 30 seconds, with a RELIABLE cruising range, over moderately hilly terrain, of at least 40 miles at 65 mph!--Bob

I'm largely in agreement with y'all. I think a lot depends on the vehicle and where you're riding/driving it.

For a restricted access highway capable vehicle (ahem) yeah I totally agree the top speed of the thing should be at least 80 miles/hr. Not that I'm going to do 80 miles/hr. I'm gonna do the speed limit or thereabouts and need that higher top speed as a safety buffer.

It also has to do with what the vehicle looks like. I experience this nearly every time I drive my Karmann Ghia. It has a 45 miles/hr or so top speed and a somewhat lackadaisical acceleration, but it looks like every other kinda car and the other drivers appear to believe it will have the same kind of acceleration and top speed as they have. It is a safety problem because my car isn't having the same acceleration they have, and it's only a matter of time before someone in a neighboring car makes a poor decision assuming my car is capable of more than it can do.

Taking a max 65 miles/hr vehicle onto a road where the prevailing consensus behaviour includes common 80+ miles/hr is the same sort of mismatch.

IMHO, it's all about road traffic compatibility. To me the term Freeway, (or motorway/UK, Autobahn/Germany, Autostrada/Italy ) are high speed roads with multiple lanes designed to maximise traffic flow, Highways are regular two-way sealed roads with a high degree of traffic flow. These roads usually have traffic speed limits around 30-60 mph (60-100kph) and most freeways are restricted to 70mph(115kph) the great exception is some Autobahn areas where speed limits are nonexistent.

EV traffic should be able to compete in both acceleration and maximum speed to integrate with the traffic flow. I realise you can drive/ride slowly, but you simply become a self-righteous frustrating safety hazard. creating safety problems for fellow road users.

NEV's are excellent in gated communities and low speed, low traffic roads, but are just pest's on the highway.

Not in a hurry? Catch a bus or train!

I recall a book being published at one time "Unsafe at ANY speed", but that was another story.....
Realistic speeds would be probably a sustained cruise speed of 75mph, with peak of 85mph (the governed speed that the average consumer auto was restricted to for a while) and an uphill minimum-bogdown-to of 65 (sustainable without damage or cutout) Of course, the chassis and suspensions should also be tuned to perform well at these speeds too, as well as the brakes. Most US roads were definitely not built on the flat, so the hillclimbing is important to figure in. (Looks back at MarylandBob's specs.... yeah, that should do it) :-)

I would never own a car or motorcycle that has a top speed equal to the maximum speed I drive/ride. With an EV the acceleration near maximum speed is atrocious due to BEMF. Plus what about the situations where you have a slight grade or headwind? Then as mentioned above there are occasions that having some extra passing power both adds safety and convenience.

EVs are perfectly capable of performance on par with ICE cars, and it doesn't do justice for the cause to build EVs that perform like icewagons. Top speed of a highway capable EV should therefor be at least 90-100mph, while carrying at least 2 adults.

FWIW, I've had my ebike as high as 61mph, but on the roads I ride I match traffic speeds by cruising at 35-45mph. I get on the highway only occasionally because while my bike can achieve the posted speed limit of 90kph (56mph), the long period to get to speed and the hill I have to cross make it unsafe in terms of not being able to match traffic speeds.

John

An EV should be able to go the highways speed limit plus a small margin - including uphill (max grades on interstates are only 6% except for a few mountain segments). However, the "need for speed" and acceleration is largely a commercially-imposed cultural thing. Most cars are overpowered these days compared to the subcompacts cars of the 1980's - the main reason cars got better fuel economy back then. Acceleration rarely, if ever gets a driver or motorcycle rider out of trouble, defensive driving does.

My e-maxs, as currently configured, have just enough speed and torque for the local city to semi-rural roads, streets and boulevards (no freeways - "parkways" as they are called in Pittsburgh) I use them on, and I'm perfectly happy with that.