Nearly a fifth of motorists (19 per cent) have unintentionally exceeded the speed limit because overgrown greenery obscured a road sign, according to a survey commissioned by the RAC.
The research found that 94 per cent of drivers taking part had encountered signage covered by overhanging trees, branches or hedges. More than half of those polled (51 per cent) reported seeing obscured signs on a frequent basis.
The issue also affects general road safety, with four out of five respondents (80 per cent) stating that untamed plants made pulling out of a junction or roundabout safely difficult. The signs most commonly affected include speed limit warnings, stop signs and give way signs.
Uncut vegetation has caused 21 per cent of drivers to miss a turn, 13 per cent to brake sharply and 5 per cent to inadvertently ignore a give way sign, according to the figures.
The RAC advised property owners to check whether any plants growing on their land have spilled on to public roads or pavements. It added that trimming them back to keep signs visible and pathways clear "goes a long way" in maintaining road safety for everyone.
RAC spokeswoman Harriet Hernando said: "It's concerning that so many drivers have broken the speed limit because they haven't been able to see a road sign that has been obscured by foliage."
She added: "While a small number have accidentally ignored a give way sign, the effects of doing so can be catastrophic."
The RAC warned homeowners that councils could ask them to remove their unpruned trees, hedges or shrubs if they are blocking a public road or footpath. A failure to do so could result in a possible fine, something more than half (58 per cent) of survey respondents were not aware of, according to the motoring services company.
Road signs that are obscured can be reported to the council or National Highways if they are on a motorway or major A-road.
The RAC commissioned research company Online95 to conduct the survey of 1,412 UK drivers in August.