So far I kept myself out of engineering discussions on STS, as the board is not a engineering board and there are many forums specifically for applied sciences and especially for chemistry, physics, electronics, engineering, machining and car building.
Also I feel your post is in the wrong subforum as a car has little to nothing to do with a garden, I shall move it to the off topic section.
To answer your question: it remains unclear what you mean by 'solar car'. If you mean a car that uses solar radiation to produce required energy in situ the discussion comes to an end when considering the current state of solar energy. Photovoltalics would be the only option one could seriously discuss for such application and at the time the efficiency and longlivety of a solar cell is by no means suitable to power a car if said car has to provide all the surface area for energy 'generation'. Further limitations would be nights, tunnels, any kinds of shadows or just bad weather, which of course could be dealt with for short time, if the solar cells would be capable of powering the vehicle at all.
Yes, experimental solar cars exist, those run in good daytime conditions but are by no means usable, safe, fast or offer any space or comfort.
Now if you are referring to a car running on electricity that has been generated off site in order to charge said car the discussion again is at its end, as electric cars do exist, just like solar energy (in this application we are free to use whatever method works best for a given geographical location [solar power plants utilize different mechanisms]).
Rednecking anything is just not compliant with regulations which to some extend make sense. Chassis should not simply be converted to electric vehicles because the battery packs will likely end up in spaces where they a) reduce usable space in the vehicle and b) mess up center of gravity. Adding a battery pack was not a design objective in the process of designing a chassis of a fossil fuelled vehicle. Also many other parts are not suitable, suspension parts might not be up to accept additional loads from heavy battery packs and so on.
There is many interesting concepts, some real bad psuedo scientific, others feasible, like adding solar cells to the general infrastructure, so a highway, upsetting the landscape anyways, could be upgraded to generate electricity from sunlight and maybe at the same time shade the highway. Also standartised interchangable battery packs could be charged at gas stations and exchanged to reduce 'charging' times, the motorist would pay for the energy in the battery pack and also cover all other expenses like the service itself and the lifetime reduction of the batteries and quality insurance etc.
Future motoring is a endless topic, alternative fuels, electric, trains, aircraft, undersea, autonomous operation, sharing jadda jadda. I guess you'll have to be more specific. But in general I'd like to point out that motoring alone is not responsible for combined emission of pollutants.
Get uncomfy and go slow: