Firefighters ordered to slow down when answering 999 calls say the new restriction could cost lives.
West Midlands Fire Service has told its drivers to keep their speeds at 45 mph in 30 mph zones and 80 mph on motorways from 1 November.
The Drive To Arrive policy is being introduced in an effort cut the number of
accidents involving fire engines.
But firefighters are concerned the rules will mean taking longer to respond to emergencies and could reduce the chance of rescuing some people from fires.
Fire Brigades Union (FBU) spokesman Pete Gallagher said: "Every time we are caught on camera the police inform the fire service and because of that we have been told that we are driving too fast.
"We are quite clear that if it is going to mean a safer environment for our
members and if the brigade feels that this does not affect the safety of the
public then we would support it."
But he added: "We don't want to see this as a back door method of reducing the number of fire engines that can turn out to fires.
"A lot of firefighters are frustrated because they feel that it will stop them getting to fires quicker.
'Excessive speeds'
"If these conditions mean we take longer to get to a fire, the chances of
somebody getting rescued could be decreased."
Vij Randeniya, assistant chief fire officer at West Midlands Fire Service,
said: "The rules are being brought in as part of a wider range of measures to
make sure that we arrive safely and on time.
"We don't believe this will make a significant difference to attendance
times.
"As we started to monitor our vehicles we saw that some fire engines were
doing excessive speeds when it was not appropriate."
He added: "There is a view that is supported by research that a vehicle travelling at a slightly slower average speed will make just as much progress through urban areas."