Even if one insists on ignoring that the majority of life-altering and season-ending injuries, as well as a substantial share of deaths occur in situations that had more to do with intersection geometry and sudden appearance of the cyclist from an unexpected direction, and instead looks only at how motor vehicle speed does indeed increase the severity of injury and likelihood of death in the minority of injurious that actually were about closing from behind.
Even if one is going to insist on ignoring those overall facts and look only at speed of closing.
Then that very same speed creates impact energy consideration has to include
how the speed of the bike-form devices is itself increased by motors. People are now getting killed in e-bike crashes that involved no other moving party at all.
And not just the impact energy, but also the reduction in time to react and evade - we see how the cyclist's own speed plays a role in most any video of a classic right hook, entering driver, or dooring tragedy.
Maybe you think the collision energy in the all-too-common case where someone moving at 10-12 mph on a sidewalk-like or curbside route collides with a vehicle turning or entering at an only slightly higher speed is an an acceptable risk - though remember what things like high clearance vehicles and aggressive bumpers can do at even moderately low speeds.
But surely even those who ignore the basics of pedal bike safety can understand how
riding a motorized device through an intersection from a sidewalk-like or curbside position at 20, 28, or 30+ mph is going to be far too dangerous.
If electrified bike-like devices are going to be meaningful car replacement then we have to look at the basic realities of the demand
- People covering American distances aren't going to be satisfied with moderate pedal assist speeds
- 20 and 28 mph "e-bikes" are what start to have car-replacement potential outside the shortest trips - and are often cheaper anyway
- many will look instead to something even faster - which should be regulated as a motor vehicle even though it is often not going to keep up with cars
- users are going to want to use the speed they have available, so offered routes must be survivable at the same sorts of speeds that ordinary traffic lanes are
Electric motors make it impossible to continue to ignore the realities of the demand for mixed traffic.
And nevermind the safety issue,
sheer numbers force mixed traffic as well - if we actually got a remotely impactful number of people out of cars, then we'd have to be using the main public transportation space to accommodate them, rather than squeezing them into the margins of public life.
5% two wheeled user mileage share means nothing in terms of reducing the climate etc impact of full size motor vehicles, and it's not "a start" if it's done in a way that cannot scale
25% percent starts to be a change - but a future with 25% bike and light electric mode share in terms of people's routine mileage travelled is one where most of the ordinary roads that go places where people need to, are going to have to see those devices operated in the same space as the cars that remain - special casing is physically impossible on too many of those routes.
A bike and light-ev future is a future where bikes and light-evs are
first class users of the public roads. Anything less is just a cute little theater skit we put on where some people are encouraged to pretend they are doing something, while society as a whole stays stuck in the very "only cars are practical" mindset that is the underlying problem.
Subsidizing e-bike purchases is brilliant politicking - it's basically a tiny "guilt fee" that society pays to pretend that it is doing something, even while in directing their users to "bike lanes" on the unsafe and impractical margins of transport space, it only doubles down on remaining car-focused.
We need a world where far from accusing a bike or light-ev user in front of them of "hogging the road" those in four wheeled vehicles recognize that it is actually their insistence on continuing to operate such which (situationally justified or not) is what is "hogging" the multi-purpose public road.