At the top end, the 20mph speed limit isn't an absolute, like the speed of light. It's just the most you'll get from the motor. I was able to get it up to 28mph on a flat road (there are no other roads where I live) in Turbo mode and 8th gear, but it took hard work to get there and maintain the speed. The easiest comparison is my mountain bike, where I've hit 23mph on that same stretch of road—and that took a heck of a lot of effort. Exactly how much effort does it take to ride? I have a 15-mile route that I ride on both my mountain bike and cyclecross bike. According to my Apple Watch, I generally burn around 1,400 or so calories on a brisk ride. I'll probably average around 13mph or so on my Marlin and between 16 and 17.5mph on my XO2. I averaged 14.9mph and burned a hair over 1,000 calories with the Bulls Cross E8.
Ebike definition in Colorado follows the HR 727 National Law: 20 mph (30 km/h) e-power and 750 W (1 hp) max, 2 or 3 wheels, pedals that work. Legal low-powered ebikes are allowed on roads and bike lanes, and prohibited from using their motors on bike and pedestrian paths, unless overridden by local ordinance. The city of Boulder is the first to have done so, banning ebikes over 400W from bike lanes. Bicycles and Ebikes are disallowed on certain high speed highways and all Interstates unless signed as "Allowed" in certain rural Interstate stretches where the Interstate is the ONLY means of travel.[83]

80% of your personal Carbon Footprint is made up of three main things. How you POWER your House. What you EAT. How you TRANSPORT yourself. There are major changes happening in all three of these areas. In the next 5-10 years, homes will have economical options to incorporate Power Generation, Power Storage and putting Surplus Power back on the Grid. …
Built around a heavy-duty alloy frame, the GSD eschews many of the traits of other cargo bikes: long wheelbases, bigger wheels, and especially, an unwieldy ride. Yet it boasts an extensive capacity, nimble handling—even fully loaded, thanks to a short wheelbase and 20-inch wheels—and enduring range in a package not much bigger than most non-cargo e-bikes. The stout frame holds a 250-watt Bosch motor that gives up to 275 percent of your power back to the pedals and reaches 20 mph. The GSD has room for two battery packs, extending the batteries’ combined range to a claimed 150 miles and making the Tern one of the longest-lasting e-bikes on the market. A laundry list of accessories and a (claimed) 396-pound carrying capacity round out the GSD’s status as an epic day-tripper.
Because the power is applied through the chain and sprocket, power is typically limited to around 250–500 watts to protect against fast wear on the drivetrain. An electric mid-drive combined with an internal gear hub at the back hub may require care due to the lack of a clutch mechanism to soften the shock to the gears at the moment of re-engagement. A continuously variable transmission or a fully automatic internal gear hub may reduce the shocks due to the viscosity of oils used for liquid coupling instead of the mechanical couplings of the conventional internal gear hubs.
This article did a good job of trying to justify the assist speed limits but fell short of detailing how that can ever be effectively enforced. In reality the only enforcement that is going to work is applied speed limits to use of bikes and ebikes. For example, it makes sense that a bike lane on a street that the speed limit of vehicles is the speed limit of the bikes/ebikes. On sidewalks and shared pedestrian paths the speed limit probably does need to be in the 15-20mph range to match traditional bikes speeds on those paths.
Built around a heavy-duty alloy frame, the GSD eschews many of the traits of other cargo bikes: long wheelbases, bigger wheels, and especially, an unwieldy ride. Yet it boasts an extensive capacity, nimble handling—even fully loaded, thanks to a short wheelbase and 20-inch wheels—and enduring range in a package not much bigger than most non-cargo e-bikes. The stout frame holds a 250-watt Bosch motor that gives up to 275 percent of your power back to the pedals and reaches 20 mph. The GSD has room for two battery packs, extending the batteries’ combined range to a claimed 150 miles and making the Tern one of the longest-lasting e-bikes on the market. A laundry list of accessories and a (claimed) 396-pound carrying capacity round out the GSD’s status as an epic day-tripper.
Simple, convenient, cheap, and economical—bicycles are one of the world's favorite forms of transportation. But they're not for everyone. They can be hard to pedal up and down hills or with heavy loads, and elderly or disabled people may find them impossible to manage. In the last few years, a new generation of electric bicycles has begun to revolutionize our idea of environmentally friendly transportation. These new cycles have all the convenience of cars with all the simple economy of ordinary cycles. Let's take a closer look at how they work. 
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