Thames Valley Police have cautioned that setting speed limits which motorists view as unrealistically low may actually worsen overall road safety.
This response comes after Oxfordshire County Council proposed reducing the speed restriction on Steventon Hill and the A4130 route approaching the Milton Interchange along the A34 from 40mph to 30mph.
During the consultation, the force indicated that merely placing new signs for the altered limit would probably fail to convince drivers who have used these roads at 40mph for years to modify their habits.
In paperwork published online before a final decision, officers also suggested that speed monitoring cameras could be installed along both stretches of road.
The paperwork read: Thames Valley Police note that when a speed limit is considered unrealistically low and routinely broken by the majority, it can undermine overall safety, erode trust in speed restrictions, and unfairly penalise motorists.
They also emphasised that police enforcement resources are limited and that regular patrols should not be expected where limits are introduced without accompanying road design modifications.
Local residents also voiced considerable opposition to the proposed reduction to 30mph, with many consultation participants feeling this would be overly restrictive given the character and function of the A4130 and Steventon Hill.
Concerns raised included the rural or non-residential nature of the route, absence of development along the roadside, and the established pattern of the road functioning at higher speeds.
Some participants observed that 40mph has historically served well and that lowering limits would unnecessarily impede traffic movement, heighten driver irritation, and damage respect for speed restrictions generally.
Other ideas being examined include creating a new bus lane on the A4130 travelling eastbound between its junctions with Steventon Hill and the A34 Milton Interchange near Didcot.
The plans additionally cover new measures stopping westbound motorists from turning around on the A413 at the Milton Interchange at the signalised junctions linking Trenchard Avenue and Steventon Hill.
Notwithstanding police objections, the council’s consultation showed that of 70 respondents, more supported the speed limit reductions than opposed them.
Oxfordshire Liveable Streets, which supports the scheme, said: Given the lack of cycling infrastructure along this section, which forms the main cycling route between Steventon and Didcot, the speed limit should also be lowered to 30mph.
The road here is wide and includes central hatching in places, which tends to promote faster driving.
Consideration should be given to removing the centre line and creating a southbound uphill cycle lane, or alternatively a bus lane where sufficient width exists.