Apart from the obvious, this raises another issue. Dropping speed limits by increments of 50km per hour or more creates problems for heavy vehicles.
NSW has a policy of doing this on main roads and highways, then placing a speed camera for good measure. Roadworks are another issue, with many private contractors seemingly lacking in common sense. If you receive a fine under these circumstances, contact Highway Advocates 24/7 on 0488-01-01-01 for obligation-free legal advice.
“Your lawyer in your pocket”