A 25mph school zone? That seems fast. 15mph would be more the norm, which is in line with the 17mph the car believed itself to be traveling.

FYI, unless you are a commerical truck, a cop, or a racer, your speedometer will read slightly fast, sometimes as much as 5 to 10%. This is normal practice for cars as it limits manufacturer liability. You can check this using independant gps, ie not an in-dash unit. (Just imagine the court cases if a speedo read slower than the actual speed and you can understand why this started.)

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lkbm 11 hours ago | parent | next [-]

I mostly see 25 mph for school zones, though I'm in NC. Checking California, it sounds like 25 is standard there as well.[0] Some will drop to 15, but 25 is the norm as far as I can find.

[0] https://www.dmv.ca.gov/portal/handbook/california-driver-han...

	▲	0xffff2 10 hours ago \| parent \| next [-]
		I've lived all over California and I agree that 25mph is the norm here. Edit: However, elsewhere in the thread someone linked this Streetview image that shoes that this particular school zone is 15mph: https://maps.app.goo.gl/7PcB2zskuKyYB56W8?g_st=ac
	▲	thfuran 5 hours ago \| parent \| prev [-]
		25 mph is typical non-school-zone residential around here, with school zones always slower.

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tastyfreeze 11 hours ago | parent | prev | next [-]

Also, a different wheel diameter than the speedometer was calibrated with and you will have a larger difference between actual velocity and speedometer reading. The odometer will also not record actual distance traveled.

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sandworm101 8 hours ago | parent [-]

It depends. I had a honda motorcycle where the speedo was 10ish % fast (not unussual on bikes due to tire shape) but the odo was accutrate. Same sensor, but the computer just counted wheel rotations slightly differently for each use.

	▲	TylerE 6 hours ago \| parent [-]
		Virtually all speedos read fast. The federal standards have a fairly high margin for being allowed to read high, and a zero margin for reading low. Thus speedos are more or less universally calibrated to read at least 5% high.

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loeg 7 hours ago | parent | prev | next [-]

It does seem fast to me -- school zones are 20 mph in Seattle, at least when children are present. But Google suggests 25 is the norm in Santa Monica, where the incident occurred.

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cardiffspaceman 10 hours ago | parent | prev [-]

In Encinitas, California, that sign would have no more than 20 MPH. In adjacent Carlsbad, I believe 25 is normal.