Does a city or village have any authority to temporarily or permanently modify highway speed limits set by state law?

Yes. Cities and villages have been granted specific authority by the state legislature to modify certain statutory limits in Wis. Stat. sec. 349.11. In some circumstances, this can be done without approval of the department of transportation. For example, a city or village may, without the consent of the department, reduce the speed limits on highways under construction as provided under Wis. Stat. sec. 349.11(10), or increase the speed limit stated in 346.57(4)(e), (f), or (g), or to reduce by 10 miles per hour or less the speed limit stated in 346.57(4)(a), (b), or (d) to (j), or to reduce by 15 miles per hour or less the speed limit stated in 346.57(4)(k). If these modifications are desired, they can be implemented by adoption of an appropriate ordinance by the municipal governing body. However, any reductions in the statutory speed limits would only become effective after a sign is properly posted in compliance with the uniform traffic control device manual, to inform the motoring public of the speed limit which the governing body has adopted.  As provided under sec. 349.11(5), Stats., the costs for placing and maintaining new signs would have to be borne by the municipality.