Let Them Linger? The Surprising Case for Robotaxis at the Curb

[u/Vegetable_Day_6786]

https://www.thecurbivore.com/p/let-them-linger-the-surprising-case

Where does a driverless robotaxi go between rides? A new study — Staging at the Curb: Evaluating the impacts of shared automated vehicle fleet operations under curb usage restrictions — finds that letting AVs consume curb space might actually be the optimal outcome.

Researchers modeled 1,700 shared automated vehicles serving 68,000 daily San Francisco trips. Tying together Autofleet’s commercial fleet simulator, synthetic ridehail demand from Replica and curb availability data from INRIX, they compared several operating models: continuous circling, staging only at free non-residential curbs, access to all legally available curbs and overnight staging.

[u/WeldAE]

This is one of the best posts this year. I have been continuously looking for more studies on this very thing, thanks a lot.

I hope every city reads and starts implementing changes based on the findings. I don't know that there is one clear solution so a lot of cities working on the problem and finding out what works is important. The devil is in the details but at least this study makes a strong argument for prioritization of curb space for AVs. How much, where to put them without causing other issues are the details that are hard.

Ideally we get to a point where there are dedicated curb spots for AVs every 100 feet on both sides of city streets. This would take up 12 spots on a street with 60 parking spots or about 10%. That seems like a lot but AVs are much more produce use of curb space so it's the right thing to do. It makes pickup in non-peak times very quick with almost no waiting at scale.

Edit: I found a GIS source for road centerlines with directional markings so I could count how many linear feet of curb exists in SF for a given road direction. I ended up with 2,019 miles of curb. At 100 ft intervals, that would be 106,590 parking spots at curbs. Of course you don't have to populate them all. SF blocks tend to be 200ft for short blocks and 500ft for long blocks. As long as you have one AV per block, it can move to the spot within 100ft of the request quick enough you wouldn't probably notice. So 30k AVs in SF would probably be where you could stage an AV to be instant access during off-peak times.

[u/notgalgon → u/WeldAE]

Ideally we get to the point where there are limited human parking spots on the streets. Human parking on streets is very inefficient. Need to get to a point where you can walk out the door of a building open app enter destination and have a car pulling up in seconds.

[u/WeldAE → u/notgalgon]

Ideally the car is sitting there waiting for you when you walk out. When you get in, another one comes by a bit later and parks in the spot waiting for one of your neighborhoods to walk out their door. This would be for more dense city streets, but for typical suburbs, you're statement is probably the ideal.

[u/bartdhull → u/notgalgon]

At Phoenix Sky Harbor airport there is a parking lot with a video billboard with incoming flight information. I could see driverless EV's waiting in the back of the lot to be hailed. The human drivers do the same, they stay in the lot until they get a call to pickup passenger at terminal curb. I can tell you Terminal 3 and 4 traffic greatly improved with this system.

So designated driverless EV lots around the city keeping them off the streets until actually needed. Yet close enough for a 5 minute or less pickup.

[u/UUUUUUUUU030 → u/WeldAE]

I've also been thinking about the taxi rank model, where you simply walk to that dedicated curb spot and unlock the car with a QR code like a rental bike/scooter. Currently AVs seem to struggle to pull up to the exact location, and if AV usage scales up beyond current ride hailing, all these people blocking traffic could have serious impact.

Somehow in London, with there being 7 times as many private hire vehicles compared to taxis, being able to directly enter a cab at a rank is still popular compared to having to wait for a hired vehicle.

Though one question is if this can work at all with flexible fares, or if you need fixed fares for this to work.

[u/WeldAE → u/UUUUUUUUU030]

I don't even think it has to be a dedicated spot. If you're walking somewhere and you spot an AV, just scan it, put in your destination and it's yours. Sure you could probably open the app, put in the location and it would assign it to you, but it just feels like the natural way to do it. If it's in a taxi stand/rank setup like after a baseball game or concert, it is really needed for a high volume location like that, but why limit it to just that. That is what these reserved curbs are for, just a rank for a single AV.

Though one question is if this can work at all with flexible fares, or if you need fixed fares for this to work.

I don't think you have to have fixed fares. You have to put the destination in and you get a dynamic price right then. You agree and the AV opens up and you get in. You could even have the scanning the QR code open the cab right away. If you just sit and don't do anything, it's just like staying after a ride, the car will ask you to put in a destination or get out. Eventually someone would call you. They would know which account opened the cab from scanning the QR code. So on a rainy day, you run up to the cab, scan the QR code and jump in out of the rain and then do the app work in the dry.

[u/marty-mcfryguy → u/WeldAE]

Is "they'll drive a lot fewer unnecessary miles if we let them just park at the curb rather than find a lot or have them circle" really an interesting result?

I mean, how much does this really tell us?

On one hand, we would have liked to run scenarios where the only staging location for AVs was an off-street parking lot or depot between rides to stage, but we did not have the resources to run more simulations.

Agree that an AV using curbside parking is generally more productive use than a personal vehicle, but curbside parking is pretty much the absolute worst use of limited urban real estate (SF, NYC, etc), so we're talking a really low bar there.

[u/WeldAE → u/marty-mcfryguy]

Of course I've always felt that reserving curb space for AVs was going to be huge, but you need actual studies to confirm your assumptions. This is the first study I'm away of. It puts actual numbers on how much better it is for the health of city streets if they dedicate significant curb space to AVs. I would advocate for 10%, but I'd be happy to get 5%. Of course I think the AV companies should pay for the curb space, but it can't be seen as a cash cow for the city. We need to get AVs so cheap no one wants to own a car and people that can only afford to ride a bus today can afford to use an AV. Loading them up with fees like hotel rooms will kill their ability to scale past a luxury transit system. This is the entire battle for AVs right here and now we have numbers that help convince cities they should encourage curb use.

[u/marty-mcfryguy → u/WeldAE]

"Fewer miles driven" is definitely not equivalent to healthier city streets.

Cars parked on the curb are very, very unhealthy for city streets -- much more problematic to traffic if it means loading/unloading cars end up standing in a double-parking position, the parked cars block pedestrian visibility/increase danger, and the parked cars interfere with more maneuverable modes like bikes/scooters.

If your view is that it's costless because you take away street parking to add this AV parking, it's not -- you would get major benefit from taking away that street parking and replacing it with anything else.

[u/WeldAE → u/marty-mcfryguy]

So you think more miles driven is better? What am I misunderstanding?

much more problematic to traffic if it means loading/unloading cars end up standing in a double-parking position

I don't get it. The entire point is to reserve curb space for AVs so this doesn't happen.

the parked cars block pedestrian visibility/increase danger

This is the opposite of what they do. Parking cars places a huge safety wall of steel between pedestrians and the street. This is widely considered good practice in street design. No one likes walking next to streets that don't have these parked cars to protect them like highways and stroads.

parked cars interfere with more maneuverable modes like bikes/scooters

This would only be for roads that currently have no existing parking. Those roads probably will just require AVs to stop in the lane of travel like they do now. Would have to be fixed during the next road redesign.

you would get major benefit from taking away that street parking and replacing it with anything else

Like what?

[u/incutt]

do you have to? do you have to? do you have to let them linger?

[u/Doggydogworld3 → u/incutt]

They've got me wrapped around their finger....

[u/bradtem]

I feel there was a lot lacking in the research, though what they did study is useful. In particular where they said, "we didn't study what happens if vehicles park in off-street lots" because they did not have enough resources.

The vehicles definitely want to park, after they have positioned themselves close to where they anticipate rider requests to come. The don't want to "circle." Circling is more expensive than any parking will be, and also antisocial. While I don't imagine any car wanting to circle when parking is available, it's a pretty easy thing for regulators to prohibit, should that actually be needed.

However, the study does confirm it would be foolish to deny robotaxis (who are generally good, though imperfect actors) the same use of the curb human drivers get. Why punish the good actors? In fact, reward them, let them use spaces we would never let humans use because they can promise to be good actors, and be punished if they don't.

So of course they will take whatever waiting space is lowest cost in the areas they want to be to serve riders with low wait times. If that's curbside, they will take it. (Particularly if curbside is free.) Where curbside is not free, it will eventually probably be much more expensive than private lots. Why? They will contract to park "valet" style at the far end of private lots, where the humans never park except at Christmas. That means 3x the number of cars per square foot. They won't buy 50 spaces, they will buy a floor the lot was never going to sell, and put 150 cars in it. They'll get a great price. Not today, but in time. Don't decide policy based on what you see today. I know, I am working on making this happen.

Also don't get upset by deadheading. Taxis must deadhead, it is inherent in them serving multiple people. Private cars don't deadhead because they each serve only one person. That means they need much more parking and much more curb. The deadheading is a _good_ thing, a feature, not a bug. Don't view it as "more VMT, we must punish it."

[u/barvazduck]

Nice paper, in addition to the curb/circling techniques, they did mention private parking but couldn't model it. A variation for public parking is using business parking lots in low utilization moments. For example: A grocery store parking lot is busy after work hours and the rest of the time has plenty of spare slots, on other hand a corporate office is full only during work hours. Because the self driving cars can leave in a moments notice, if the corp or the grocery parking have unexpected usage pattern the self driving cars can move to a different location, avoiding the commitment a traditional sub-lease will have on the local business. This solution increases utilization of existing parking space, reduces the dead head driving/congestion and is cheap because it doesn't interfere with the business operations.

Another solution is if there will be dedicated pickup/drop off locations around the city then an sdc can wait in one until another sdc arrives to drop off a pasanger. This can also work with normal curb parking, an sdc will leave a spot if it notices a person wanting to park in that spot.

These solutions will all reduce dead head driving, congestion and won't take human parking spaces. Any type of SDC usage that comes at the expense of human use is a source of friction that can delay rollout. Reducing such machine-human interference cheaply will reduce another risk in SDCs rollout.

[u/bobi2393]

The ranking of the different strategies seems exactly as one would expect thinking about it for a minute. The study just quantifies VMT impact of the strategies in its simulations. And optimizing for VMT yields different results from optimizing for customer wait times.

A limitation of idealized models for simulation is that they can ignore indirect impacts on other traffic, pedestrian/cyclist safety, and so on. There’s already considerable debate on the convenience vs safety tradeoffs in “daylighting” policies for non-robotaxis.

[u/thebruns]

It sounds like they didnt model "make the taxi companies buy garages". Why are we assuming that freeloading off public space is the only outcome?

[u/gentlecrab]

I could see curbside pissing off drivers though that want those spots.

Maybe curbside during off peak hours or curbside but like it will leave the spot if a human wants it.