The RAC says some drivers took advantage of the emptier roads to drive at "dangerous speeds" – including in residential areas.
Department for Transport data shows cars and light vans travelled at an average speed of 36.2 mph on 'A' roads in the area last year – an eight per cent rise on the average of 33.5 mph in 2019.
The A689 Belle View Way saw the biggest rise in speeds – up 50% to an average of 54.3 mph – followed by the A179 road to the A19, which saw average speeds rise by 27% to 44.9 mph.
Nationally, the average speed of cars on 'A' roads rose by eight per cent last year to 27.3 mph – caused by a steady increase in speeds following the Covid-19 stay-at-home restrictions in March last year, the DfT said.
Simon Williams RAC road safety spokesman, said the impact of the pandemic was "a double-edged sword".
He added: "On the one hand, fewer delays is positive and may well have led to an improvement in overall air quality, but on the flipside, we know that some drivers have taken advantage of quieter roads by driving at dangerous speeds."
Mr Williams said it is important police forces continue to crackdown on excessive speeders and that there are consequences for their "totally unacceptable" actions.
The Department for Transport said average speeds are returning to pre-pandemic levels as Covid-19 restrictions continue to be eased.