Hybrids/Alternate-fuels

The Internal Combustion Engine is a complex, amazing machine. In perfect concert, valves open, spark plugs ignite, pistons move, and the crankshaft turns. Every fourth cycle an air-fuel mix explodes and a piston is forced down. The crankshaft converts the linear motion of the piston and connecting rod to rotational motion that eventually propels the vehicle. (Tesla Motors) 

Tesla model S

Most people say that conventional engines can't be beaten; they're tried, tested and reliable. But these people don't realise that, in theory, an electric car is better for several reasons.
1) More space. Due to the fact that an engine isn't needed, an electric car can have two boots (one where the boot should be, and one where the engine should be) and the batteries can go where the petrol tank, undersides of the car and bottom of the engine should be, to keep an even weight distribution,
2) More torques. Electric motors generally have more torque because they just do. A lot of normal engines only get peak torque nearer the top of their rev range, whereas an electric motor can give 100% of its torque instantly. This means that electric cars are quicker off the line than their petrol counterparts, hence why some top-of-the-range supercars are electric (Tesla Roadster, McLaren P1 and Porsche 918)
3) Instant horsepower. Again, because the motors can deliver 100% of the torque at once, they can do the same with the power. (read above) 
4) Very little/no road tax. Electric cars tend to have such cheap road tax because they don't push out any emissions, except for the few that have a small petrol engine to charge the motors (Vauxhall Ampera) This means that the UK government won't charge you to use the roads (theoretically).

Although there are a few good points to electric cars, there are some down points too, such as

Vauxhall Ampera

1) Limited range. Usually about 100 miles or so, a pure electric car can't go that far on one charge. Some cars are improving this by putting a small petrol generator in the car to keep the batteries topped up, but getting the range of a normal car is still a long way off
2) High costs. A hybrid will cost a LOT of money to initially buy, even with the government grant. A base model Vauxhall Ampera is £30,000 (£25,000 after the grant) which is a lot of money for the car, the equivalent petrol model is a lot cheaper. 

Typical LPG conversion

LPG powered cars are another viable alternative to conventional petrol cars. These use Liquid Propane Gas instead of petrol to power the car. It works by having 2 tanks in the car, one for petrol in the normal place, and one for LPG which is usually situated in the spare wheel well. The Car starts up and runs for a few minutes on petrol before seamlessly switching to LPG, and running just like a petrol car would whilst using it. If you then run out of LPG, the car can seamlessly switch back to petrol again, and give you a warning that you need to refill your LPG. I think LPG is a good idea, mostly because the price of it is almost half that of petrol, and second-hand LPG cars can be just as good as ones with brand-new conversions (LPG is an aftermarket modification) without paying the near £1000 cost for the conversion. 

Thinking about these points then, why don't car manufacturers make petrol-electric hybrids in the style of the Vauxhall Ampera that also have LPG conversions. A tiny petrol tank (I'm talking motorbike sized) just to get the engine stared and up to temperature when it is needed, and an LPG tank to run the engine on. The motorist will have to pay virtually nothing for the LPG, charging of the batteries and would still get the range that these hybrids are offering. Even using the £5000 government grant after buying a hybrid to convert it to LPG can't be too hard, and it is essentially being done for free. Quite frankly, I'm amazed I don't see more of this happening.