Politicians have blocked plans for roundabout advertising that could have earned Herts County Council thousands of pounds each year.
The authority had wanted to install four posts at the Chesham Road entrance to Berkhamsted, which would be seen by drivers as soon as they leave the A41.
But Dacorum Borough Council’s development control committee decided at a meeting on Thursday that planning permission for the signs – on which firms would display their logos – should be refused.
The borough councillors said the signs would distract drivers and endanger youngsters walking to Ashlyns School, also based on Chesham Road.
Councillor Fiona Macdonald said: “From September this is going to be a main route with lots of children aged 11 and 12 crossing that road.”
The school will accept an extra 570 pupils in Years 7 and 8 from the next academic year as Berkhamsted switches from offering three- to two-tier education.
Tom Ritchie, speaking on behalf of Berkhamsted Town Council, said cars approach the roundabout – at the junction between Chesham Road and Kingshill Way – at speeds of up to 60mph.
He said: “Authorised fly-posting is what this is and we already have a problem with fly-posting in this area.”
The meeting heard that the roundabout was in the Green Belt and that plans for similar signs on the other side of the A41 junction had previously been rejected.
Councillor Rosmarie Hollinghurst said: “How much money are they going to get to destroy our view of the countryside just to make a few quid?”
Councillor Ian Reay said that the signs could earn between £1,000 and £2,000 a year for the county council.
Meeting chairman Graham Sutton, who himself sponsors a Dacorum roundabout on behalf of his business, said the figure was even higher.