Dropping the speed limit down to 25km/h when emergency vehicles are under red & blues's also presents an additional risk of "secondary accidents" in certain circumstances.
For example, a car is driving along a section of freeway in medium to heavy traffic with a posted limit of 110 km/h. There is fog patches about and it has been raining. The road starts turning through a bend to the left, just on the apex red and blue lights become visible. What should the driver do?
Brake hard to slow down from 110 to 25 could risk skidding / loosing control or be hit by other vehicles traveling behind.
Now I hear you say that they should be driving to the conditions. I challenge anyone who has had to respond to an incident on the SE Freeway to say that ever happens!
Best solution is for enough police to provide traffic control further back to give prior warning of the incident ahead and to allow a progressive reduction of speed. How often do we ever see this able to be done? Even with the current level of 40km/h it is still an issue we have to consider and input risk control measures, this often take the form of crew members being used solely as safety observers looking out and provide a warning should they see a wayward vehicle.
You don't hear me say "They should be driving to the conditions" but you will hear me say "Darcyq, go and read SACFS Operational Bulletin 25/2010 - Road Traffic Management"
Ops Bulletin 25/2010 clearly states that the "Taper Zone" should begin 165m from the Work Zone in a 110 km/h Zone. This is easily achievable with multiple resources on scene. It also states that among other things, weather and road topography must be taken into account, prior to setting up a traffic management zone. Any IC with half a brain should be switched on to this and manage the scene accordingly.
You can't simply park your appliance and expect everything to be fine. Its all about creating safe zones, and acting under the assumption that motorists will not slow down.
If all else fails shut the road until SAPol have enough resources on scene to manage traffic appropriately.