Just like on London's famous Underground, or the New York subway, handicapped people in Congo's capital Brazzaville get discounts on public transport.
While the discounted ride won't get them to Buckingham Palace or the Brooklyn Bridge, it has helped them make money, as they carry goods across the broad Congo river for traders who want to avoid paying full fare.
"With this, we don't have to beg. If we didn't have this, what would we do?" said Maman Hortense, who has been paralysed since childhood.
The river connects Brazzaville with Kinshasa, the capital of the neighbouring Democratic Republic of Congo.
The twin-city metropolis of more than 10 million is teeming with small traders, dependent on traveling between the two banks and all desperate to avoid the bureaucratic crossing fees that cut into their income.
The cost of a return trip across this three-kilometre (two-mile) stretch varies widely, as fees are randomly applied and corruption is rampant on both sides, a World Bank study said.
Many residents told AFP they usually manage to pay no more than 30 euros ($21) for a return trip, though they can find an even cheaper -- but more hazardous -- crossing in dugout canoes or pay a pricier fee on luxury speed boats to avoid queuing.
Taking in the variations, the World Bank set the average round-trip fare at $40, noting this is nearly half the monthly income of most area residents. To drive home the impact, it compared the Brazzaville- Kinshasa crossing to one of similar distance across the bay that separates San Francisco from Oakland, California.
"If, relative to local average income, the same costs applied, San Francisco residents would pay between 1,200 and 2,400 dollars for a return trip to Oakland," the study said.
But the situation opened a niche -- if not always an easy one -- for the local handicapped. In sub-Saharan Africa, where social services are abysmal and the disabled are often treated as semi-outcasts and the poorest of the poor, their services are in high demand at the 'Brazza'-'Kin' crossing.
When a boat coming from Kinshasa docks, dozens of people disembark and climb up to the port, known locally as the Beach, hoping to cram through customs so they can start selling their goods.
Sometimes porters race with crippled people on their backs, while a flock of other porters clad in numbered jackets unload packages to carry on their backs or their heads.
"Before, it used to be more spectacular," a European resident of Brazzaville said. "There was a barge, Le Matadi, with a gate. When it opened, the rush was like the Normandy landings!"
"Le Matadi is broken down today," a port official told AFP.
"There are several ways of doing business. If you simply want to cross, you can recruit a blind man or another disabled person and be his guide," a policeman explained.
"Your ticket will be half as expensive as the full price and you give a part of what you saved to the disabled person," the policeman said.
Rather than being "hired" by able-bodied merchants, some handicapped work as traders themselves, benefiting from the lower "fees" and "taxes" afforded to disabled people on each package of goods transported across the river.
Barthelemy Bassumba, 32, who has been paralysed in the legs and confined to wheelchair since childhood, was one who used to run his own business. While he apparently suffered from polio, he prefers to tell people that he was the victim of witchcraft linked to "a family problem".
His trade collapsed, however, and he started working for others who pay him for each crossing.
"I don't do any more business myself. Once I sold my product, beer, to a man who never paid me. I lost 100,000 FCFA (150 euros)", he recalled, noting that he earns 120 euros a month to support his wife and two children.
Baggio Ngama Bamba of Kinshasa, who has a deformed leg, also uses his disability to make a living, but he said the stresses of trading across this hectic river are becoming unbearable for him.
"We buy produce in Kin, we sell it here in Brazza. When we make a profit, we give money to those who help us," he said.
"But now there is too much hassle, taxes and outgoings. It's too much. We can't make it any more."