A Highways England document seen by Transport Network has revealed worrying levels of speeding on the strategic road network (SRN).
The national road operator said: 'Sadly with the declining volume of traffic we have also noted an increase in speeds on the SRN.'
In a message to a local resilience forum, Highways England noted that major motorways including the M6, M5, M42, M40 – 'have all seen some substantial rises in speed'.
Increases in speed limits following roadworks and completed schemes would not be promoted by Highways England out of fear that the speeding could put further pressure on the NHS at this time, the document said.
A London Assembly Member has also written to transport secretary Grant Shapps calling for an emergency reduction in national and urban speed limits to reduce demand on the NHS.
The proposed emergency speed limits would see the default national speed limit cut to 50mph and the default urban speed limit cut to 20mph.
Green Party member Caroline Russell took the step after police were forced to respond to excessive speeds over the Easter weekend.
She said the 20mph urban limit would be especially useful in London, which has seen a shift in the way people, including key workers and NHS staff, are travelling during the coronavirus crisis.
Ms Russell said: 'Londoners are doing their best to protect those key workers who have to take public transport by staying away wherever possible and making their own essential journeys on foot or by bike.
'They are doing their bit and it is the Government’s duty to make these journeys safer – we must have a lower default speed limit to protect people walking and cycling.
'This will have threefold benefits, protecting key workers making essential journeys on public transport, reducing the number of collisions and therefore pressure on our already pressured emergency services AND crucially protecting people walking and cycling.'
These changes are possible as emergency national legislation and similar measures have been adopted previously in response to shortages of fuel, she said.
No further road signage should be necessary, but Ms Russell supported a public information campaign to make road users aware of changes, and enforcement of new speed limits, in her letter.