The Age of Electric Vehicles

[dyqik]

https://jech.bmj.com/content/early/2024 ... 024-221902

During 2013–2017, casualty rates per 100 million miles were 5.16 (95% CI 4.92 to 5.42) for E-HE vehicles and 2.40 (95%CI 2.38 to 2.41) for ICE vehicles, indicating that collisions were twice as likely (RR 2.15; 95% CI 2.05 to 2.26) with E-HE vehicles.

Looks like they need to be made noisier - to protect pedestrians.

Another factor is that EV/HEs might be that they have longer braking distances. I've been unable to find out whether this is in fact the case, there seems to be some disagreement about it.

They shouldn't have worse braking distance than the highway code etc. suggests. Separately, emergency braking distance is a function of tires and suspension, and driver alertness, not drive train type. Weight only comes into it if the tires and brakes don't match up to vehicle weight.

The use of high efficiency tires might increase stopping distances, but so does worn tires, etc.. Against this, most EVs include collision avoidance driver assistance features that older ICE vehicles don't. And noise from passenger vehicles doing 30 mph is at least as much road noise of tires on road as engine noise. It's only at low speed that engine noise is important - when fatalities are much less likely.

But for older electric hybrid vehicles in the 2013-2017 time frame, I suspect that there's a confounding factor of the kind of people who drove those vehicles vs the general driving population. Priuses, etc. have a particular image and market segment they includes quite a few older people, as well as taxi usage.

[Woodchopper]

https://jech.bmj.com/content/early/2024 ... 024-221902



Looks like they need to be made noisier - to protect pedestrians.

Another factor is that EV/HEs might be that they have longer braking distances. I've been unable to find out whether this is in fact the case, there seems to be some disagreement about it.

They shouldn't have worse braking distance than the highway code etc. suggests. Separately, emergency braking distance is a function of tires and suspension, and driver alertness, not drive train type. Weight only comes into it if the tires and brakes don't match up to vehicle weight.

The use of high efficiency tires might increase stopping distances, but so does worn tires, etc.. Against this, most EVs include collision avoidance driver assistance features that older ICE vehicles don't. And noise from passenger vehicles doing 30 mph is at least as much road noise of tires on road as engine noise. It's only at low speed that engine noise is important - when fatalities are much less likely.

But for older electric hybrid vehicles in the 2013-2017 time frame, I suspect that there's a confounding factor of the kind of people who drove those vehicles vs the general driving population. Priuses, etc. have a particular image and market segment they includes quite a few older people, as well as taxi usage.

I suspect that typical usage patterns maybe part of the explanation. The study compared accidents per million miles of driving. During the period being studied range anxiety meant that electric cars were more likely to be used on short urban journeys whereas ICE cars were more likely to be used on long cross country journeys. Most accidents are in urban areas where people live, and not on motorways etc used for long distance driving, and engine noise will also affect accidents at low speeds, but not motorway accidents. The difference between electric and fossil fuel cars may reduce over time as electric cars are now used more frequently for long distance journeys.

[dyqik]

The range part wouldn't apply to hybrids though (my 2010 Prius gets 450-500 miles range on highways).

[FlammableFlower]

New EVs definitely have to have a sound emitted if the vehicle is going slowly - although interestingly, the government regulations around this state:

From 1 July 2019, all manufacturers must install a system in new types of quiet electric and hybrid electric vehicles. Sound generators will produce a specified level of noise when they are reversing or running below 20 km/h (about 12mph). The sound generated will be similar to that made by a conventional engine and can be temporarily deactivated by the driver if judged necessary.

Mine kicks in below 19 mph. Above that the road noise is pretty much equal to any other ICE vehicle. I can't switch it off temporarily, but in my previous, 2018 Zoe, I could.

Just conjecturing, there are two possible issues, both around problems with familiarity with ICE vehicles not translating to EV - one being the speed of acceleration; I generally keep mine in Eco mode as I've found it's otherwise ridiculously easy to spin the wheels pulling away, but even then with Eco, the 0-30 acceleration is much better than most ICE vehicles. So yes, people do underestimate the time they have to pop across a road, for example.

The other issue is with familiarity with engine noise. We've had so much exposure to ICE vehicles that the sound of an engine is very familiar to people and so hearing that sound automatically gives a subconscious indication of a vehicle in proximity and taken into account. Whereas with EVs, even with the emitted noise, there's a lack of familiarity that might not necessarily have the same effect. My car has the "choir of damned" sound (as some have termed it, being choral and quite eerie) and it's pretty loud (my kids have complained about how it sounds from outside - e.g. when I'm arriving at home), but I definitely notice that if I'm approaching pedestrians from behind, and it's narrow/lot's of parked cars etc, then they often don't appear to take any notice until I'm in their peripheral vision. Seeing as it's definitely audible, I'm putting it down to a lack of association with proximity to a car.

I'm not convinced just being noisier will help.

However, there are other issues around noise - first, older EVs often don't have fitted noise generators and even those with them can be inconsistent. My neighbour's Tesla has no forward noise (it may be pre-2019), but will generate a sound when reversing. Whereas, my newer Zoe is the opposite - oddly it's silent in reverse, which I think is daft.

Overall, it seems like the government regulations and guidance aren't much cop.

[Gfamily]

The data is relatively old, and from a time when EVs were very much a minority, and with it based on casualties per 100k km, it's hard to know how they ensure that the km metrics are comparable.
For example, the 98% of the casualties were from ICE vehicles rather than EVs, so the EV casualty rate would come with higher uncertainty.
In the 'confounding factors' it suggests that young drivers (who present a higher risk of being involved in collisions) are more likely to drive EVs than the average driver, but that is based on 2023 data (regardless of the fact that asserting that over 40% of young drivers have EVs, seems improbable to me at least).

[bob sterman]

I suspect that typical usage patterns maybe part of the explanation. The study compared accidents per million miles of driving. During the period being studied range anxiety meant that electric cars were more likely to be used on short urban journeys whereas ICE cars were more likely to be used on long cross country journeys. Most accidents are in urban areas where people live, and not on motorways etc used for long distance driving, and engine noise will also affect accidents at low speeds, but not motorway accidents. The difference between electric and fossil fuel cars may reduce over time as electric cars are now used more frequently for long distance journeys.

The study looked at urban and rural driving separately.

E-HE vehicles were three times more dangerous than ICE vehicles in urban environments (RR 2.97; 95% CI 2.41 to 3.7).

[Woodchopper]

I suspect that typical usage patterns maybe part of the explanation. The study compared accidents per million miles of driving. During the period being studied range anxiety meant that electric cars were more likely to be used on short urban journeys whereas ICE cars were more likely to be used on long cross country journeys. Most accidents are in urban areas where people live, and not on motorways etc used for long distance driving, and engine noise will also affect accidents at low speeds, but not motorway accidents. The difference between electric and fossil fuel cars may reduce over time as electric cars are now used more frequently for long distance journeys.

The study looked at urban and rural driving separately.

E-HE vehicles were three times more dangerous than ICE vehicles in urban environments (RR 2.97; 95% CI 2.41 to 3.7).

Well that should teach me not to idly speculate