Traffic chaos which after a key route flooded must never happen again, city leaders have demanded.
Birmingham roads bosses have been told to set up pre-planned diversions to avoid a repeat of last month's gridlock when a underpass flooded.
This flood on the A34 Birchfield Road saw drivers unable to move, vehicles break after being stationary for hours and people forced to abandon cars to walk into town.
A report into the chaos, which was caused by a pump power failure after heavy rain, has demanded a string of measures to avoid a repeat.
The flood was discovered by police and road contractor Amey at 8pm on Monday, October 13, and the road closed shortly afterwards.
But, incredibly, no warnings were issued to the media and traffic news services until 7.30am the next morning – too late to avoid rush hour chaos which quickly ensued.
The report also discovered pumping equipment to get rid of the water had to come from Bristol, more than 90 miles away.
The underpass is fed by four major commuter routes bringing traffic from the M6, north west Birmingham and Walsall, making it one of the key arteries into the city centre.
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At the time angry drivers lashed out, saying no-one was on hand to divert traffic or warn motorists early enough to take alternative routes.
Coun Jon Hunt (Lib Dem Perry Barr) said the council and its partners were woefully unprepared for the incident and needed to take more decisive action as winter approached.
He said: "The report shows the night crew failed to raise the alarm in spite of closing the road overnight. This may not happen again and commuters might get earlier warnings.
"But it still seems very peculiar that, having closed the road, no emergency procedures were put in place. The first radio broadcast wasn't until 7.30am.
"I am still concerned the council does not understand the massive impact the gridlock had on many people who were held up for periods of up to four hours.
"It is vital that traffic is diverted early and from as far back as Walsall and Birmingham city centre when the A34 is closed in this way during rush hours."
The Birmingham Lib Dem deputy leader said the report had failed to consider bus companies which who would need to implement diversions and warn passengers of delays.
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"We've had three weekends of heavy rain since this event and a great deal of flash flooding.
"As we go into the winter, residents will expect more decisive and effective actions to deal with emergencies such as this."
A Birmingham City Council spokeswoman said: "We will be looking at the cost benefits of having pre-planned diversion routes as part of a package of measures. However, the crucial issue is finding out about the problem as early as possible so motorists and other commuters can be made aware as soon as possible."
The report, following an investigation by contractor Amey, found that, with the pumping station under water, it took hours to identify power failure as the cause and the electricity firm Western Power did not arrive to restore power until the Tuesday afternoon.
It also found that temporary pumping equipment to clear water was not readily available, being supplied from a firm in Bristol. A nearer source has now been found.
It highlighted failures of night duty stuff to alert bosses to the closure and send prompt warnings out to the media. The city council has welcomed the report and promised to act on recommendations.
Cabinet member for transport Tahir Ali said: "It is vital to understand what happened and ensure these problems aren't repeated. While we can't prevent a power failure, we can ensure our response is as quick and efficient as possible.
"I'm pleased to see that some of the recommendations have already been completed, and others are in progress.
"The key recommendation that has been completed is the installation of a remote monitoring system that will detect a power failure."