A town in the US has banned cyclists on most of its streets, punishing anyone who gets caught with a $68 (£46) fine. Black Hawk in Colorado, which has a population of just above 100, is thought to be the first town in the US to make cycling illegal after a change in civic law.

The curious decree has been introduced for "health and safety" reasons, said administrators of the former goldmining town, which in the 1990s decided to develop gambling to prevent the place vanishing altogether.

Michael Copp, Black Hawk's city manager, the equivalent of chief executive of a local council in the UK, admitted there had not been any accidents to prompt the ban, just concern over potential collisions between motor vehicles and bicycles on 19th-century streets that were designed for horses and carriages.

The town started enforcing the ban on 5 June, five months after it passed the law requiring cyclists to dismount and wheel their bikes through the town. So far eight tickets have been issued, said Copp.

Copp, who does not cycle himself, said the council passed the ordinance after the town experienced a surge in traffic – buses, delivery trucks, and motorists – following a law that increased the maximum betting limits from $5 to $100 once it chose gambling as its raison d'etre.

The ban applies only to the narrow 19th century thoroughfares in a town that is lined with historic buildings and new casinos, not the few residential streets. Cyclists riding in on Colorado highway 279, a main route through the town, would have to dismount and walk about 400 metres, Copp said.

"This ordinance is necessary for the preservation of health and safety and for the protection of public convenience and welfare," says the law, which is set out on the Black Hawk website.

"The rules will allow bicycle traffic that originates locally to continue to operate with City Manager authorisation, while still assuring that such traffic can operate in a manner that is not incompatible with vehicular traffic," says another clause.

Cyclists' lobbies are gearing up to challenge the law, which they say is illegal.

"The danger here is the precedent," Dan Grunig of Bicycle Colorado, an advocacy group, said. "We don't believe it's right or legal and we want to make sure it's addressed before it's spread any further."

Grunig's group, which claims 7,000 members statewide, has appealed to national groups to help.

"An outright ban on being able to ride a bicycle through a community is unheard of in any other community in the country, said Charlie Zeeger, director of the Pedestrian and Bicycling Information Center at the University of North Carolina.

But Black Hawk seems proud to be first. "At this point the council has no intention of repealing the ban," Copp said. "They believe their actions are what's best for its citizens in Black Hawk, which are casinos and their patrons."