Don't think of it as replacing what historically was walking outside and hailing a cab, think of it as setting up a carpool with office mates except you don't have to know them, and you don't have to work out all the details, it will be handled for you.
Mass transit works well in dense areas because the vehicles are large and only need to go short distances or go long distance over a specific route. When everyone has their own custom route, person A's route may make person B's route unacceptably longer. Also, sitting on a bus/train with 50 strangers is less of an odd social situation than sitting in a car with one stranger.
Once autonomous cars get to the point where they don't require any driver attention at all, I think it will make ownership even more appealing since you could customize the entire to match whatever you want to do while you're hauled around.
Everyone has their own door as well so there isn't as much jostling past and touching and being touched by strangers even in a full car.
The only time I've ever taken an Uber or Lyft and I not have my own door and/or I've had to scoot past people is in large party situation and those other people were my friends.
I've talked to women and they seem to prefer an Uber or Lyft over taking the train and/or the bus. Also, being dropped off at your destination rather than walking a few blocks from a metro stop to where you are going also makes a massive difference.
The benefits really outweigh the drawbacks. Especially if this is cheaper than owning one's own car. In theory, a private automated car service (calling a car and being the only rider) would still be cheaper than owning a private car and still have the same conveniences. It's just that eventually it will basically just be 4x cheaper to share a ride.
Mass transit remains the most viable method of transporting people over dense, multi-mile terrain.
The last mile and "normal" metros like Memphis, Baltimore, or Cleveland, where it is not dense enough to justify a comprehensive subway/light rail system, are probably the best use cases for self-driving cars and universal car sharing systems.
There is at least one lane on either side of the road at full capacity. Always bumper to bumper. But, the cars do not move save 2% of the time when their operators remove them from the traffic jam, I mean parking spot. There are 275,450 streetside parking spots in San Francisco city limits. Assuming a pooling of some drivers, and an increased utility of roads due to size & traffic flow then we can look forward to a net decrease of cars on roads and a net increase of available land for expanded sidewalks and bike paths.
Rail mass transit does not as efficiently use the land it's on a occupancy basis (there's not always a train on a specific square foot of track). In peak times, cars are more efficient on a vehicle basis. According to BART system facts[1], there are 107 miles of track. There are 669 cars, seating for 72 in 448 of them with each being 70 feet (with 59 of them having an additional 5 feet for a cab), and seating for 64 in 230 cars[2] (with an indeterminate car length, so I'll use the smaller listed), for a total capacity of 46,976 seated people. BART states that all cars can hold over 200 people in a "crush" load, so we'll assume 200 as the theoretical maximum, and say BART can carry 133,000 people when at peak (crush) capacity, and over the 107 miles of track, that gives us a density of 1,250 people per linear track mile, but with only 8.3% track utilization at any one time.
Cars do not as efficiently pack people per vehicle usually, but can more efficiently use the roads on a per-vehicle basis. Assuming very heavy traffic which is not stop-and-go, so perhaps 35 miles an hour average (the same as BART), and a 4-lane highway (two each direction), if each car is allowing two car lengths between itself and the car in front (slow traffic), we have approximately 33% road utilization (or 25%, or 20% depending on what you think the average space between vehicles is). Since carpooling seems to be at about 10% currently carpooling[4] (ignoring that it may be different in certain arterial routes, as we are discussing), we have around 1.066 people per car[5] as a lower bound. With an average car length of 177.2 inches[6], or 14.77 feet, we can estimate the people per mile on the highway during this time as being 604 people per mile of 4-lane highway.
Interesting take-aways for me:
While 4-lane highways may take more room than rail (not sure the actual sizes here), they are also more versatile.
If the highway bogs down below 35 mph, it's then less than the average rate of BART, and we need to start computing people over time instead of just people over distance.
BART has much more room to increase track utilization, but there is likely unaccounted for overhead here on each train. Optimal usage at current speed is one train arriving immediately after the prior one leaving, at 35 mph exact speed and 20 second stops, for a train of six cars (?) and 425 feet, that would be cars 2.42 train lengths apart, and a utilization of 29%, or roughly a 4x increase over current rates, 5,000 people per track-mile.
Cars have much more room to increase vehicle utilization. If we replaced 50% of vehicles with full size vans transporting on average 7 people each and didn't touch road utilization, we would be at an overall average of 4 people per car, and 2600 people per highway mile. Interestingly, if we somehow moved towards a system where smaller vehicles picked up and shuttled people with small amounts of sharing to bus-stations where they were sorted into smaller buses (40 people) going specific area depots, and from those depots dispersed again to final destinations using individual cars with small amounts of sharing, we might easily surpass rail transit systems. averaging 20.5 people per vehicle, but with somewhat more area used should put us close to 10,000 people per highway mile.
Of course, there's a lot of assumptions in all the numbers, and some speculation in the possibilities, but I thought it was interesting to figure out. ;)
1: http://www.bart.gov/about/history/facts
2: I know the total car numbers don't add up. Complain to BART, it's their data.
3: (66970 feet + 695 feet)/(7 * miles * 5280 feet/mile) = (47125 feet)/(564960 feet) = 8.3%
4: https://www.census.gov/prod/2011pubs/acs-15.pdf, table 1.
5: 105,476 drove alone, 13,917 carpooled, if we assume all carpooling was just two people per car, we get person to car density by (105,476+13,917/2)/105,476 = 1.066 people per car
6: https://www.reference.com/vehicles/average-length-car-2e8538...
7: 5280 feet/mile / 14.77 feet/car * 0.33 highway mile utilization = 117 cars at highway lane mile utilization. 117 cars * 1.066 people/car = 126 people per mile of highway lane. 4 lanes fives us 604 people per highway.
People do it already to save money. Making it easier, and adding the ability to set up a standing appointment with the same people over multiple days would alleviate a lot of people's concerns, IMO.
> Lots of people still have relatively specific needs, e.g. requiring car seats of various sizes for their young children, needing to pick-up or drop-off kids at school, sports practice, etc.
Many families have two cars, purely because of the few times a day when both are needed at the same time. For example, I have a Honda Odyssey for family use, since I have three kids. I also have a cheap commuter that I lease, purely to get to and from work a few times a week, since I work from home a couple days. That's a car I could happily and easily remove from service with little impact, as long as I had a way to get to and from work.
> When everyone has their own custom route, person A's route may make person B's route unacceptably longer.
The idea is, with thousands of routes, you might find quite a few that overlap a significant percentage of the time. Compute what percentage each person is responsible for of the whole, subtract some portion of the route for the distance that's spent going to the other pickups/dropoffs that aren't on your path, and provide a a discount depending on how much you share. Use minivans and/or full-size vans if there are enough rides to maximize people, comfort and space. The carrier maximizes profit over people and vehicle wear over a ride, and the people minimize price.
> Once autonomous cars get to the point where they don't require any driver attention at all, I think it will make ownership even more appealing since you could customize the entire to match whatever you want to do while you're hauled around.
Sure, but that's a luxury use. People that drive luxury cars that cost a lot will undoubtedly do that. People that are trying to minimize cost so they can spend that money on essentials or even just other luxuries they value more will opt for the cheaper option. It's why people carpool now.
Why not just keep your partition up between you and the other passengers? Because no human driver needs visibility out all of the windows, you can split the car into private spaces. When no driver is needed, it opens up a lot of different configurations.
The self-driving vehicle needn't be a small car.
