Bike sharing in African cities has lagged due to lack of dedicated lanes and the perception that cycling is for the poor, worsening traffic jams and pollution, experts said on Wednesday.

Bike sharing has expanded across North America, Europe and Asia as authorities seek to boost the health of city residents and the planet, but it has struggled to take off in Africa where road networks tend to favour motorists.

"When governments only construct highways for vehicles, they are conditioning people to own cars," Amanda Ngabirano, an urban planner at Uganda's Makerere University told the Thomson Reuters Foundation on the sidelines of a Nairobi bike sharing forum.

"The attitude towards cycling is still bad across Africa. It is seen as a poor man's form of transport and has been pushed aside by planners."

Morocco's Marrakech was the first African city to get a bike share programme in 2016 with the support of the United Nations as it prepared to host a climate conference.

Experts are keen to increase cycling across the continent as it could reduce traffic jams and air pollution and enable more people to get around their cities, improving job opportunities.

"Simultaneous to building infrastructure is building a bicycle culture, by raising awareness on the benefits that cycling can bring to people's lives," said Stefanie Holzwarth, a mobility expert at UN-Habitat, an urban development agency.

Sitting in Nairobi's notorious traffic jams costs 1.6 billion shillings ($16.2 million) a year in wasted time and fuel, Kenyan academics calculated in 2013, a problem which is likely to worsen as its population grows.

Kenya's capital has a longer commuting time than many global cities, with four in 10 people walking because they cannot afford public transport, according to the United Nations.

But the lack of bicycle lanes makes it dangerous for cyclists who fight for space with motorbikes, cars and trucks, said Cyprine Mitchell, a transport planner with the New York-based Institute for Transportation and Development Policy.

"Infrastructure in many African cities is a barrier to cycling," said Holzwarth. "There is fear among many people that would like to cycle because the infrastructure is not safe."