This story was originally published on September 7, 2018.

Besides making it super-easy to get a ride somewhere, one of the great promises of ride-hailing services like Uber and Lyft was that they would reduce congestion in city streets as more people left their cars at home and shared with others.

Traffic consultant Bruce Schaller is the former head of the traffic and planning division at the New York City Department of Transportation. (Submitted by Bruce Schaller) Unfortunately, the opposite has happened — and dramatically so, said transportation consultant Bruce Schaller

Schaller, the former head of the traffic and planning division at the New York City Department of Transportation, recently investigated the impact of ride-hailing services on congestion. And the results are not encouraging.

It turns out that the majority of ride-share app users are not people who would otherwise drive their car, but people who wouldn't have driven a car in the first place.

"Most people say, 'I would have taken the bus, the subway, the metro, walked or biked or sometimes, I wouldn't have made that trip,'" Schaller said.

Moreover, the fact that the ride-hailing cars have to come and get their passengers actually means more mileage.

"If I call Uber to pick me up, the driver has to come to my house and then drive me there. So there's a time between trips and mileage between trips that are additional miles to the roadway."

And it's not like the ride-sharing cars get off the roads when they're aren't driving someone.

"Last year, 40 per cent of the time Uber and Lyft vehicles don't have a passenger in them. That's really inefficient," Schaller said.

All of this prompted the city of New York to cap the number of ride-sharing cars allowed on the road, at least for one year. There are well over 50,000 ride-share cars on the streets of New York already.

It's hoped the cap will "stop the influx of cars contributing to the congestion grinding our streets to a halt," Mayor Bill de Blasio said in a statement.

London Mayor Sadiq Khan has also asked for legislation to cap the number of ride-hailing vehicles in his city, calling their increase an "unsustainable rise."

40 per cent of the time Uber and Lyft vehicles don't have a passenger in them. That's really inefficient. - Bruce Schaller

Schaller said the cap might reduce congestion as it's limiting the overall number of vehicles on the streets. But he added that it's likely the existing cars will simply be on the road longer.

There is some hope, however, in a recent announcement from Uber that it plans to introduce electric scooters and bikes for hire, which might be an incentive for people who would otherwise book a car.

"During rush hour, it is very inefficient for a one-tonne hulk of metal to take one person 10 blocks. Short-term financially, maybe it's not a win for us, but strategically long-term, we think that is exactly where we want to head," Uber CEO Dara Khosrowshahi said.

Schaller agreed. "They're a much more efficient use of scarce street space than a vehicle."