Speed limit signs could swing down on pivoted arms, so they are at the eye level of oncoming drivers. The sign could come down a fixed distance ahead of the driver, or immediately after the preceding vehicle, whichever is less.

The sign retracts a moment before the time at which the vehicle's windscreen would have reached the sign had the vehicle been travelling at the limit. A metal tooth mounted at the bottom of the sign protects it from being hit by the intact windscreen of speeding vehicles.
-- pocmloc, Jun 29 2019

Seriously, a spritz of murky water and a sudden loud honk could do the trick.
-- pashute, Jun 30 2019


Look up from the mobile, get shocked by a road sign, lose control and crash through a school.
-- wjt, Jun 30 2019


<getting the obvious joke out the way quickly>passing aggressive road signs, which tut as you roar past them. </gtojotwq>
-- calum, Jul 01 2019


These signs will encourage games of 'chicken' with drivers concentrating on driving at a speed such that the sign *just* avoids hitting their windscreen
-- hippo, Jul 01 2019



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