A new bill introduced in the Oregon Legislative Assembly aims to prohibit the operation of Class 3 electric-assisted bicycles on sidewalks, bicycle lanes, and
With E-bikes it’s not just the “unnaturally” fast speed but also weight and that’s doubly important for powered cargo bikes.
Speed limits don’t really make sense here though. What determines the amount of damage inflicted in a collision or how easy it is to avoid a collision by breaking is kinetic energy; that’s what needs to be limited.
I’d just base this around what a “normal” human on a “normal” bicycle can do on flat ground with reasonable human power alone: e.g. 70kg human on a 10kg bicycle doing 25km/h. That’s 80 kilogram × (25 kilometre / hour)² = 3858.02 J of kinetic energy.
Now we can assume e.g. a 20kg e-bike and calculate backwards: sqrt(3858.02 joule / (70 kilogram + 20 kilogram)) = 23.5702 km/h
Or with a 50kg cargo e-bike: sqrt(3858.02 joule / (70 kilogram + 50 kilogram)) = 20.4124 km/h.
Ideally cargo bikes would also factor measured load into them. If you carried an additional 50kg, it should only power up to 17.1498 km/h for instance.
What conditions would be “safe” under “normal” circumstances and how heavy you assume people to be are debatable and dependent on where you are (welcome to NA, +10kg avg. weight) but the mechanism should be the same.
We need to define some limit of kinetic energy that is reasonably safe for pedestrian and bicycle collisions and in line with what typical human on an unpowered bicycle would net you. Powered bicycles (or any other powered vehicle for that matter) then need to enforce that limit by way of cutting off power once the maximum kinetic energy is reached.
While velocity is certainly the larger contributor, it’s not like mass is insignificant either. Especially for the cargo bike case where even unloaded the mass difference requires a ~5km/h change in velocity for equal kinetic energy.
When you get to very high absolute velocities, mass becomes less and less significant but we’re very much at the low end here in that regard.
With E-bikes it’s not just the “unnaturally” fast speed but also weight and that’s doubly important for powered cargo bikes.
Speed limits don’t really make sense here though. What determines the amount of damage inflicted in a collision or how easy it is to avoid a collision by breaking is kinetic energy; that’s what needs to be limited.
I’d just base this around what a “normal” human on a “normal” bicycle can do on flat ground with reasonable human power alone: e.g. 70kg human on a 10kg bicycle doing 25km/h. That’s
80 kilogram × (25 kilometre / hour)² = 3858.02 Jof kinetic energy.Now we can assume e.g. a 20kg e-bike and calculate backwards:
sqrt(3858.02 joule / (70 kilogram + 20 kilogram)) = 23.5702 km/hOr with a 50kg cargo e-bike:
sqrt(3858.02 joule / (70 kilogram + 50 kilogram)) = 20.4124 km/h.Ideally cargo bikes would also factor measured load into them. If you carried an additional 50kg, it should only power up to 17.1498 km/h for instance.
What conditions would be “safe” under “normal” circumstances and how heavy you assume people to be are debatable and dependent on where you are (welcome to NA, +10kg avg. weight) but the mechanism should be the same.
We need to define some limit of kinetic energy that is reasonably safe for pedestrian and bicycle collisions and in line with what typical human on an unpowered bicycle would net you. Powered bicycles (or any other powered vehicle for that matter) then need to enforce that limit by way of cutting off power once the maximum kinetic energy is reached.
Speed’s contribution to kinetic energy is exponential, whereas mass is just a direct multiplicative component.
So speed is absolutely the largest contributing factor.
Your equation actually highlights a good point where that speed should be kept.
While velocity is certainly the larger contributor, it’s not like mass is insignificant either. Especially for the cargo bike case where even unloaded the mass difference requires a ~5km/h change in velocity for equal kinetic energy.
When you get to very high absolute velocities, mass becomes less and less significant but we’re very much at the low end here in that regard.