Ed Pawlowski wrote:
> "Dave Smith" > wrote in message
>> Speed limits are upper limits, not lower limits.
>
> \
> Check this
> http://en.wikipedia.org/wiki/Speed_l..._United_States
>
> http://ideas.repec.org/a/eee/transa/...9p767-775.html
> This paper presents the results of the mail out survey conducted in the
> United States to unveil the current state of practice related to the posting
> of minimum speed limit signs on Interstate freeway system. The analysis of
> the survey results has revealed that half of the country (25 states) posts
> the minimum speed limit on Interstate freeways. The most common posting is
> 40Â mph. There are few states that post 45Â mph and 55Â mph in some sections
> on Interstate freeways. The survey results has also discovered that many
> states raised the maximum speed limits on Interstate freeways as the
> consequence of the National Highway System (NHS) designation Act of 1995
> without revising or studying the effect of the existing minimum speed limits
> on traffic operation. Implications for future research relates to a multi
> state study which will evaluate the relevance of minimum speed limits on
> speed variability that is created by the posting of minimum speed limit.
>
>

So it would appear that 25-30mph under the speed limit is an offence in
some places, not 15.