Here is a brief quote from Wikipedia:"Electric cars were popular in the late 19th century and early 20th century, until advances in internal combustion engines, electric starters in particular, and mass production of cheaper gasoline vehicles led to a decline in the use of electric drive vehicles."

Good as this entry is, it is incomplete - no discussion of the 1914 Prius.....

From a mechanical engineer´s point of view the headrest was designed the way it is: removeable and with a sharp edge on the prongs. It saves smoothing up to four edges and designing and building an unneeded retention device. That is money saved and therefore money earned.
Designing it as a safety feature would require proof that it will work reliably and can be deployed with enough ease over the service life of the vehicle. That would create significant extra costs with no real benefit.


If it saves only a few people that´ll be enough. Surviving a ditch in the water makes one a probable customer for a new car. That´s a clear win-win situation.

Inquiring minds want to know, so I plodded out to my Sentra and inspected the headrest. The twin prongs are nicely chamfered at a 45 degree angle (impeccable Japanese crafsmanship)- wouldn't want the owner to get any nasty gashes or cuts which could result in expensive lawsuits....

"If it saves only a few people that´ll be enough" has a nice ring to it, but some sort of rescue tool will probably be far more effective. Rather than wrestling with my headrest, I am more likely to use the Phillips head screwdriver on my Leatherman tool. It will likely be far more accessible.

That may really depend on the pride the manufactures take in their product. I have seen some with a sharp edges too. It´s a matter of manufacturing costs though.



It´s not intended as rescue tool. Some headrests cannot even be removed from an upright seat.

I prefer what they do in my country. New cars are delivered with two rescue tools as standard. One for each front seat.

Not sure if it's law or not, but have not seen newer cars without.

again, preparing for something which is pretty unlikely.

Snopes classes this as 'mostly false':

http://www.snopes.com/car-headrests-emergency-escape/

qjs

Thanks for the link, quick joey!

I think a more accurate way of describing it is ( if you don't have anything else, try to use the headrest to break the glass, since, luckily, it is detachable !!) instead of ( it was made detachable for the purpose of breaking the glass )