"Medical Exemptions" are also a standard right in the State of Texas for motorcycles & even bicyclists. Through Texas's motorcycle helmet law (bicycle helmet laws from city ordinances), it is only required for those 21 years old or younger to wear a helmet. However, a medical exemption,  written by a certified licensed medical physician or licensed chiropractor, which exempts one from wearing a helmet, can be used for bicyclists if helmets are required.
Federal law in the United States states that an electric bicycle must have a top speed under 20 mph and a motor which produces less than 750 watts/1 hp. They are not considered motor vehicles by the federal government and are subject to the same consumer safety laws as unassisted bicycles. Their legality on public roads is under state jurisdiction, and varies. See the main Electric bicycle laws article for details on the law in individual states.
There are individuals who claim to have lost considerable amounts of weight by using an electric bike. A recent prospective cohort study however found that people using e-bikes have a higher BMI. By making the biking terrain less of an issue, people who wouldn't otherwise consider biking can use the electric assistance when needed and otherwise pedal as they are able. This means people of lower fitness levels or who haven't cycled in many years can start enjoying the many health benefits E-bikes have to offer. 
There are two main categories when choosing an e-bike: a pre-built electric bike or a custom e-bike conversion. Prefab electric bikes come in a wide variety of setups and styles and are designed specifically as electric bicycles. With unique characteristics and design qualities, most meet the law requirements which limit power and speed. There is also a variety of options to choose from equipped with different design and different motor and battery configurations to suit different riding styles and preferences: cruisers, commuters, mountain bikes and more. Pre-built e-bikes are clean and sleek in design with all of the wiring and electrical components built directly into the bike. For most people, production e-bikes work great and there’s no need for a custom conversion.
As electric bike options continue to expand, more brands are integrating the battery more seamlessly. That makes them look sleeker (and more like a real bike). Batteries are expensive, so make sure there’s a good way to lock the battery to your bike if you’ll be keeping it outside. Overall weight is important. Some battery and motors can add 15 pounds or more to the bike. With assist, you won’t feel that much when you’re riding, but you will if you have to carry your bike up stairs or lift it onto a bike rack.
The drivetrain begins with pedals which rotate the cranks, which are held in axis by the bottom bracket. Most bicycles use a chain to transmit power to the rear wheel. A very small number of bicycles use a shaft drive to transmit power, or special belts. Hydraulic bicycle transmissions have been built, but they are currently inefficient and complex.
Mid-mounted system means that the electric motor is not built into the wheel but is usually mounted near (often under) the bottom bracket shell. Mid-drive systems tend to feel more like a normal bike, since they drive the pedals, just like your legs, and those who frequently climb long, steep hills tend to prefer mid-drive systems for their ability to handle long climbs. As they can leverage the bicycles lowest gears for climbs, mid drive systems can also leverage the high gears to reach higher speeds on flat areas than a hub system. The mid-drive motor drives the crank, instead of the wheel itself, which multiplies its power and allows it to better take advantage of the bike’s existing gears. If the rider changes the gears appropriately, the motor can turn closer to its ideal rotations per minute which makes a huge difference while climbing hills, so this is a perfect option for those who love mountain biking.
As of May 19, 2009, Nevada amended its state transportation laws to explicitly permit electric bicycles to use any "trail or pedestrian walkway" intended for use with bicycles and constructed with federal funding, and otherwise generally permits electric bicycles to be operated in cases where a regular bicycle could be. An electric bicycle is defined as a two- or three-wheeled vehicle with fully operable pedals with an electric motor producing up to 1 gross brake horsepower and up to 750 watts final output, and with a maximum speed of up to 20 miles per hour on flat ground with a 170-pound rider when powered only by that engine.
The Wavecrest Tidalforce M-750 was based on The original military experimental M-313 model. The M-313/M-750X was the first electric bike to be made and tested by Wavecrest Labs. It is based on a design developed for the Defense Advanced Research Projects Agency (DARPA) that was meant to allow zero-heat long distance troop movements for the United States Marine Corps in Afghanistan. The rear wheel in-hub motor and 36 volt/8ah front-hub battery were mounted onto a standard Montague Bicycles Paratrooper Bicycle frame. The 1000 watt rear hub motor had no set speed restriction, but was limited to about 25-32 (depending on load weight) MPH on a flat course. The distance the bike traveled on a single charge ranged from 15 miles (heavier load with no pedaling) to about 25 miles (vigorous assisted pedaling with less hill climbing).
That being said, It is fun to ride - my 13 year old grandson likes it a lot. I feel it is best used on hard surfaces like sidewalks and hard floors. I received this little scooter 3 days ago and have ridden it in Costco and Sam's club and took it to an art show and sale as well as driving it through hospital halls on the way to and from a meeting.. One has to
Firstly there's a magnetically-fired locking pin in the rear wheel, triggered by kicking a button on the hub. This is fairly secure in itself and almost impossible to remove without destroying the bike. In London, we'd pair it with a more traditional bike lock so there's a more obvious visual deterrent, though a LED matrix screen on the frame does issue a warning to would-be tea-leafs.