Director of Public Health in Sheffield Greg Fell said the Government needs to assess each of the four steps in the roadmap in order to cautiously ease the lockdown restrictions in the country.
And the five weeks stipulated for each step aim to give some "clear blue water" to enable and assess what has been the impact of step one of the lifting of the restriction at the start of next week, when schools fully reopen.
He said: "This is very clear. Five weeks is the minimum and there are four tests to enable in the roadmap.
"The four tests set out the assessment of what has been the impact of lifting the previous set of restrictions of lockdown such as hospitalisation, vaccination, infection and the virus variant."
In fact, said Greg, the process of easing the lockdown restrictions could be slower than expected, as this depends on the outcome of the first step.
"I think we will know in about two weeks after March 8, where we will have an upward infection - there are no two ways about it.
"It will make it a bit more difficult to work out what is going on, but I think it is unlikely, almost impossible that the steps will go through quicker than set out in the roadmap."
On February 22, the Government published four-step roadmap to ease restrictions across England and provide a route back to a more normal way of life
Each step needs to be assessed against four tests before restrictions ease, starting with the return of schools on March 8.
Prime Minister Boris Johnson said that the decision on each stage will be based on data not dates, and government will move cautiously to keep infection rates under control.
However, experts have called for lockdown to be eased more quickly as the coronavirus case numbers in the UK are better than expected.
On March 2, the death rate has dropped by 37 percent in a week with 343 fatalities recorded.