Why Can't We Drive on Yom Tov?
Q. If you start a car before yom tov, why can't you drive it on yom tov as you are allowed to add to an existing flame?
A. Thanks for your question. I don't know enough about the workings of an internal combustion engine to address the mechanical aspects, so I'll refer that question to a colleague and try to get back to you with some details. I do know that a car, whose primary purpose is transportation, is a kli shemelachto l'issur (an item whose primary purpose is prohibited) and is therefore muktzeh even for short distances (like a bicycle). Second, driving is certainly uvdin d'chol – a weekday activity, which is to be avoided on Shabbos and yom tov. Additionally, there is the likelihood of the car requiring maintenance, which is the reason instruments were prohibited on Shabbos and yom tov. So, there are three reasons that do not involve the specifics of the engine. Nevertheless, I will inquire as to reasons that directly involve the acts of ignition and/or extinguishing. (The advisability of leaving a car idling for the better part of 48 hours is another matter.)
[Later…]
My colleague adds:
"Every time you tap the brakes the light turns on and off.
"Every time you use the blinkers you are turning light on and off.
"Every time you open or close the doors.
"How about turning off the engine?
"Cars are complicated machines, and pressing on the gas does more than spray gasoline into an engine. There are all types of computer controls. spark plugs...."
He's absolutely right about the lights (as well as the computers, etc.). Even if you turned off the dome lights and used hand signals, it would be illegal to disable your brake lights.
He also mentioned the possibility that one might go outside the techum (this is why a car is a kli shemelachto l'issur, as I mentioned above), and that it's a zilzul (disgrace to yom tov). I'll explain.
Did you know that one may not turn on a machine like a dishwasher or a laundry dryer before Shabbos or yom tov, allowing it to operate into Shabbos or yom tov? This is because the sound of the machine operating is considered a "disgrace" to the holy day. This is not a modern law based on our automated machinery; the gemara prohibits starting a mill before Shabbos and letting it continue to grind on Shabbos.
Finally, even if all the other issues were somehow accounted for, how would others know that you started the car before yom tov? I think there would still be an issue of maris ayin.
As my colleague said, there's a lot more going on here than just starting the engine.
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