Do Regulatory Signs trump general laws?

[CtrlAltDel]

What about the current situation with the tollways in Illinois? If I understand correctly, the state legislature passed a law raising the speed limits on these highways to 70. In response, the Tollway is in the process of raising its speed limits, but it is doing so in a piecemeal way and not always to 70. If my understanding is correct, then, in this case, the signs on the road have more authority than the statutes, but I recognize that there are competing authorities here that muck things up a bit.

[wxfree]

What about the current situation with the tollways in Illinois? If I understand correctly, the state legislature passed a law raising the speed limits on these highways to 70. In response, the Tollway is in the process of raising its speed limits, but it is doing so in a piecemeal way and not always to 70. If my understanding is correct, then, in this case, the signs on the road have more authority than the statutes, but I recognize that there are competing authorities here that muck things up a bit.

On the matter of the question about whether signs trump laws, I'd say the answer is no.  A sign cannot require or authorize a thing that is not allowed under law.  Speed limit laws are generally written so that there is a default, sometimes a higher maximum, and a provision for changing a limit.  In Texas, the laws of which I'm pretty familiar with, the default speed limit for a rural state highway is 70.  Setting a different limit requires a speed study.  The maximum (except under specific provisions) is 75.

A quick look at the Illinois code shows that the default for rural Interstates and tollways is 70, except that certain counties may adopt ordinances setting a lower maximum speed limit.  The language of the statute starts with "Unless some other speed restriction is established under this Chapter," which means that the speeds stated are default values and can legally be changed based on other statutory authority.

Section 11-603 authorizes the Toll Highway Authority to establish a different speed limit on the basis of an engineering and traffic investigation.  The signs for lower limits do not supersede statute, but are authorized by it, so long as they are based on traffic engineering principles.