The motoring organisation's analysis of Home Office figures shows the number of officers fell in 30 out of 42 force areas in 2015.
In total the number of dedicated roads officers outside London dropped by 352 (5%) with the biggest falls in West Yorkshire, Avon and Somerset, and Northamptonshire. That means the total outside the capital has fallen by 27% to just over 3,900 since 2010.
Pete Williams, the RAC's head of external affairs, says: "Overall, these figures make for grim reading and are likely to be met with dismay by law-abiding motorists.
"While some of the numbers may be explained by organisational changes, such as officers taking on multiple roles and police forces working in partnership to tackle crime, the data still clearly shows that a majority of forces have seen a further fall in the number of officers whose primary responsibility is tackling crime on our roads."
The figures raise questions, Mr Williams adds, over how the National Police Chiefs' Council will meet its commitment to tackle the biggest causes of serious accidents - speed, drink and drug driving, not wearing a seatbelt and driving while distracted.
He says: "We are acutely aware that the police are doing their best to manage challenging budgets and scant resource; however the sustained reduction in roads policing officers is at odds with the consistent number of serious motoring offences being committed and the concerns already expressed by motorists around the lack of visible police presence on our roads.
"These findings also beg the question whether forces are increasingly turning to technology to enforce the law. Fixed speed cameras are a common sight on many roads, including on the hundreds of miles of highway being upgraded to smart motorways.
"However the majority of motoring laws that exist to make our roads safer still rely on a physical officer present to either apply the law, or deter drivers from committing an offence in the first place."