Limiting One's Patience

I may have remarked before upon the taxi-driving classes.

http://pseudograph-pseudography.blogspot.com/2009/06/taxing-ones-patience

I may have referred too to the difficulties some men seem to have with etiquette when driving.

http://pseudograph-pseudography.blogspot.com/2010/07/vespax-vobiscum.html

So let me ask...

Why is that taxi drivers have no problem understanding "limit on public spending", "limit on personal taxation" and "limit on immigration", but "speed limit" seems to be completely fucking beyond them?

I only ask.