Electric bicycles have two main methods of operation: pedal-assist and/or throttle-control. As the name implies, pedal-assist “assists” your pedaling and requires some input. With this method, a torque sensor picks up movement or stress to determine the power requirements of the rider. Everything is automated so there’s nothing to think about, just jump on and start riding. Some bikes have multiple settings, while others have just one setting with the addition of a throttle control. Depending on the setting, pedal-assistance can help a little – or a lot. At lower settings, pedal-assist is barely noticeable but helps extend your range. At higher settings, the power is quite obvious and feels like a strong wind at your back with the motor doing most of the work while you pedal along.
"Bicycles" and "Electric Bicycles" are legally defined in the Texas Transportation Code Chapter 551., titled "Operation of Bicycles, Mopeds, and Play Vehicles" in Subchapter A, B, C, and D. The following definition of electric bicycle was passed by the Texas legislature in 2001. "Electric bicycle" means a bicycle that is designed to be propelled by an electric motor, exclusively or in combination with the application of human power, cannot attain a speed of more than 20 miles per hour without the application of human power; and does not exceed a weight of 100 pounds. The department or a local authority may not prohibit the use of an electric bicycle on a highway that is used primarily by motor vehicles. The department or a local authority may prohibit the use of an electric bicycle on a highway used primarily by pedestrians.
I found that by sticking it on 'Turbo' or 'Sport' mode (the upper 2 of the 4 electrical assistance levels) and leaving it in a middle gear, the Centros felt zippy when in full flight, but able to pull away from the lights with no problems. Less lazy riders than me might want to actually use the 10 gears, and will find that in the top gear, it's quite easy to push past the mandated 15.5mph electrical limit.
The pedals on a motorised bicycle must be the primary source of power for the vehicle. If the motor is the primary source of power then the device cannot be classed as a motorised bicycle. For example, a device where the rider can twist a throttle and complete a journey using motor power only without using the pedals, would not be classed as a motorised bicycle.
When you have the electric motor turned on, it engages with your first push of the pedals. The difference in acceleration is startling compared to any other bike I've ridden. In Eco mode, I could sprint from 0 to 20mph in about 200 feet/65m. Switch to Turbo, and it's about 150/30m feet. As I mentioned above, you still have to pedal. The difference with an electric bike is the feeling of getting more bang for the buck. And if you want to be lazy, you can. Stay in third or fourth gear and you'll be able to stay around 18-19mph with minimal effort. But if you want to go much faster than 20mph, you'll need to work.
Electric-assisted bicycles are treated as human-powered bicycles, while bicycles capable of propulsion by electric power alone face additional registration and regulatory requirements as mopeds. Requirements include electric power generation by a motor that cannot be easily modified, along with a power assist mechanism that operates safely and smoothly. In December 2008, The assist ratio was updated as follow:
Some power-on-demand only e-bikes can hardly be confused with, let alone categorised as, bicycles. For example, the Noped is a term used by the Ministry of Transportation of Ontario for e-bikes which do not have pedals or in which the pedals have been removed from their motorised bicycle. These are better categorised as electric mopeds or electric motorcycles.
Rad Power’s lineup of 2019 bikes start at $1,699 (there’s also a Cyber Monday special on their 2018 models), proving that electric bikes don’t have to be over $2,000 to have the amenities and quality you need for daily commuting. Of course, that’s still a steep price for some. But as prices keep dropping in the e-bike industry, affordability breeds better access, and this might be the key that our cities—and their traffic—so desperately need.
Connect the battery to the speed controller and the throttle. Follow the instructions included with the kit to connect each part. Typically, you’ll only need to plug the connector on the speed controller into the connector on the battery, then repeat the process for the throttle. Be sure not to touch the battery wires together, as this could create a dangerous spark! 
Operators are subject to driving rules and equipment requirements (if applicable) when operated on the public streets or highways (which includes the main traveled portion of the road, shoulder and sidewalk). This means that an operator could be cited for speeding, failure to signal, unsafe change of course, driving on the sidewalk, DWI (this would apply to anywhere in the state and not just the streets/highways), and all other driving rules contained within state law that would apply. They may also not ride more than two abreast and may not impede the normal and reasonable movement of traffic. On a laned roadway, they must operate within a single lane.
The Ohio Revised Code 4511.01  distinguishes motorized bicycles and mopeds from motorcycles or scooters by describing them as "...any vehicle having either two tandem wheels or one wheel in the front and two wheels in the rear, that is capable of being pedaled and is equipped with a helper motor of not more than fifty cubic centimeters piston displacement that produces no more than one brake horsepower and is capable of propelling the vehicle at a speed of no greater than twenty miles per hour on a level surface." One brake horsepower converts to 0.75 kW, or (rounded) 750W. Thus, a bicycle with an electric helper motor operating under 750W, and not propelling the bicycle over 20 mph, does not qualify to be registered under Ohio state law. Local jurisdictions may have other regulations.
In addition, Kalk weighs under 155 pounds — less than half of traditional motorbikes. Cake customized parts of the drivetrain and implemented an interior permanent magnet (IPM) motor. On a single charge, the bike travels up to 50 miles and as a bonus feature, maintenance is minimal due to the fact there are few moving parts thanks to its lack of a combustion engine.
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.