Electric motorized bicycles can be power-on-demand, where the motor is activated by a handlebar mounted throttle, and/or a pedelec (from pedal electric), also known as electric assist, where the electric motor is regulated by pedaling. These have a sensor to detect the pedaling speed, the pedaling force, or both. An electronic controller provides assistance as a function of the sensor inputs, the vehicle speed and the required force. Most controllers also provide for manual adjustment.
In 5 years of working as a bike messenger in Minneapolis, I've ridden all kinds of bikes, in all kinds of weather. I've ridden walmart mountain bikes, 80's classic steel road bikes, kitted out Treks, pretty much everything EXCEPT for fat tire bikes. Such wide tires always seemed... too much. No need for a bike that only makes itself worthwhile maybe two months out of the year, I thought.

On a trip to Palo Alto last year, we had the chance to ride Specialized’s pedal-assisted Turbo Vado and the model is still our favorite ebike on the market. Utilizing a 350-watt motor and 604-watt-hour lithium-ion battery, the Turbo Vado is capable of traveling a whopping 80 miles on a single charge, which should be more than enough for any daily commute with plenty of miles left over.
Electric bikes (also known as e bikes) are perfect for long-distance riding, or when you just don’t feel like giving your full effort. What differentiates them from electric motorcycles is the ability for the rider to pedal the bike at any time, so if you’re riding along and your battery dies, you’re not going to stranded. These are often very valuable bikes, but some models can be more affordable than you might expect, especially when you treat them as a form of transportation as opposed to thinking of the price in terms of regular bicycles.
(15.5) "Electric assisted bicycle" means a device with two or three wheels which has a saddle and fully operative pedals for human propulsion and also has an electric motor. For such a device to be considered an electric assisted bicycle, it shall meet the requirements of the Federal Motor Vehicle Safety Standards, as set forth in 49 C.F.R. Section 571, et seq., and shall operate in such a manner that the electric motor disengages or ceases to function when the brakes are applied. The electric motor in an electric assisted bicycle shall:
While I would have loved to see some higher end components such as disc brakes or built-in lights, the bike still works well for what you get and is a pretty good value for the price. One missing component that I feel would make a big difference is a kickstand. I’ve never seen an e-bike that didn’t come with one, outside of ultra premium multi-thousand dollar road and downhill e-bikes that try to save every gram of weight. But for a commuter, a kickstand is pretty important. You can always add a cheap $7 kickstand from Amazon, but I would have preferred they save us the step and include their own cheap kickstand.
Some US companies, notably in the tech sector, are developing both innovative cycle designs and cycle-friendliness in the workplace. Foursquare, whose CEO Dennis Crowley "pedaled to pitch meetings ... [when he] was raising money from venture capitalists" on a two-wheeler, chose a new location for its New York headquarters "based on where biking would be easy". Parking in the office was also integral to HQ planning. Mitchell Moss, who runs the Rudin Center for Transportation Policy & Management at New York University, said in 2012: "Biking has become the mode of choice for the educated high tech worker".[66]
Attitudes to electric bikes have changed in recent years. For a long time they were seen by cyclists as 'cheating' and by non-cyclists as being just like a bike, but uglier and far more expensive. This new breed of best-in-class electric bikes feel more natural, look more normal, and people are coming around to the idea that a ride with the convenience of a bike but without all the sweat and effort is a Very Good Thing. 
None of this would matter if the VanMoof Electrified S2 (and its close relative the X2) wasn't fun to ride, but it is a blast. Like the Brompton, it pulls off the neat trick of powering you along but giving the illusion that you're doing the work, reacting quickly and cleverly to the speed of your pedalling and the difficulty of any incline you're on. 
It's a solid e-bike, but it's also very heavy one for a folding bike. I found it difficult carry when the bike is folded as the carrying handle is useless, and the center of gravity is towards to the rear wheel so one has to find a place in the rear of the bike to pick it up. Even when the bike is folded, it's bulky and heavy, It's difficult to walk with it while carrying it. It's easy to hurt one's back if he or she is not careful. I would not recommend carrying this bike up or down stairways.
"Bicycles" and "Electric Bicycles" are legally defined in the Texas Transportation Code Title 7, Chapter 551 entitled "Operation of Bicycles, Mopeds, and Play Vehicles" in Subchapter A, B, C, and D.[131] Under Chapter 541.201 (24), "Electric bicycle" means a bicycle that is (A) designed to be propelled by an electric motor, exclusively or in combination with the application of human power, (B) cannot attain a speed of more than 20 miles per hour without the application of human power, and (C) 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[132] 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.
It appears Tennessee has not passed any legislation that applies to electric bicycles. Some people think the laws pertaining to a Motorized Bicycle should be used for an electric bicycle. However, a Motorized bicycle would be a gasoline powered device per state law as it is defined as "means a vehicle with two (2) or three (3) wheels, an automatic transmission, and a motor with a cylinder capacity not exceeding fifty cubic centimeters (50cc) which produces no more than two (2) brake horsepower and is capable of propelling the vehicle at a maximum design speed of no more than thirty miles per hour (30 mph) on level ground." [56]
We'll start this off with the latest two Customer Profile videos. In the first one we follow up from the well received Leigh Cross video with a look at his son, Tig Cross. Tig's been refining an original bike concept combining the best parts of an ebike, scooter, and velomobile, and showcases the merits of an electric generator for the human drivertrain.
On the other hand, the battery doesn’t lock into the bike, which means you can’t just leave it on your bike when you park at the bike rack. Anyone could walk by and simply remove your battery. That seems like an oversight to me, though perhaps the designers assumed that such a small battery would just be easy to take with you. And it is. My wife could probably lose this battery in her purse.