Self driving cars are still subject to the laws of physics... unless you're going to dictate that self-driving cars never go above 15mph, I wouldn't advocate jumping in front of even a "perfect" self-driving car.
Braking distance (without including any decision time) for a 15mph car is 11 ft, for a 30mph is 45 ft. Self driving cars won't change these limits. (well, they may be a little better than humans at maximizing braking power through threshold braking on all 4 wheels, but it won't be dramatically different)
So even with perfect reaction times, it will still be possible for a self-driving car to hit a human who enters its path unexpectedly.
Once upon a time when I was learning to drive, one of the exercises my instructor used was to put me in the passenger seat while he drove, and have me try to point out every person or vehicle capable of entering the lane he was driving in, as soon as I became aware of them. Every parked vehicle along the side of a road. Every vehicle approaching or waiting to enter an intersection. Every pedestrian standing by a crosswalk or even walking along the sidewalk adjacent to the traffic lane. Every bicycle. Every vehicle traveling the opposite direction on streets without a hard median. And every time I missed one, he would point and say "what about that car over there?" or "what about that person on the sidewalk?" He made me do this until I didn't miss any.
And then he started me on watching for suspicious gaps in the parked cards along the side that could indicate a loading bay or a driveway or an alley or a hidden intersection. And so on though multiple categories of collision hazards, and then verbally indicating them to him while I was driving.
And the reason for that exercise was to drive home the point that if there's a vehicle or a person that could get into my lane, it's my job as a defensive driver to be aware of that and be ready to react. Which includes making sure I could stop or avoid in time if I needed to.
I don't know how driving is taught now, but I would hope a self-driving system could at the very least match what my human driving instructor was capable of.
Sounds like you had a great driving instructor. Although I never had an experience like that when learning to drive, we did have to complete something in the UK called a "hazard perception test"[1] in order to get a drivers license. Basically a video version of what your instructor did for you. Until reading your comment today, I'd never really put much thought into how useful this is and how ingrained in my everyday driving it is.
A thing I like to do to stay in practice is to browse /r/roadcam over on reddit. I open a video at random and watch it, and try to guess where the collision (or near-collision) is going to come from.
That sounds like a great exercise, I wish it was standard. But I'm guessing you must have taken this course in a rural area, or else be able to talk faster than an auction caller. I don't think I could list off all the hazards in an urban area fast enough. :)
Good point -- there's a 4% chance of fatality when struck by a 15mph car versus 20% at 30mph.
There's a 30mph city street near me where cars routinely go 45mph -- the fatality rate jumps up to 60% at that speed. So just having cars follow the speed limit would go a long way toward reducing fatalities.
I'm greatly in favor of a slower-moving but more efficient automotive network. How many human inconveniences are caused by what boils down to impatience? See: gridlock, people entering intersections they cannot leave, and jamitons.
(IMHO) jamitons would dissolve if people would leave a flexible buffer between them and the car in front of them and focusing on minimizing braking, rather than driving up to their bumper, brake, wait for moving, accelerate, brake, repeat. The lag due to reaction time and ac/deceleration exacerbates the "viscosity" of traffic flow. If most drivers focused on "staying fluid" rather than hurry-up-and-wait, traffic ought to improve. Like fluidized beds.
I'd like to think that the economic cost of regularly killing people on the streets is higher than getting to a place ten minutes faster. American traffic fatalities per year are basically equivalent to killing off a large town.
No one is saying reduce speeds everywhere. But in an urban context with lots of pedestrians, these speeds matter, and urban traffic is generally so stop-and-go and congested that drivers rarely sustain the top speed, and reducing it doesn't actually affect travel time by all that much.
"I'd like to think that the economic cost of regularly killing people on the streets is higher than getting to a place ten minutes faster."
However comforting that logic may be, it is unusable in the real world. If you value lives infinitely, then you will never ever do anything that risks your or somebody else's life in order to gain on any other need. You routinely engage in things that are not the safest possible option in order to fulfill other needs, ranging from food or water acquisition through mere entertainment. Therefore you place a finite value on your life. Don't feel bad, so does everybody else. It is possible to determine the value placed on life, I believe there are studies that show the value is more stable than you might think, and balance things appropriately.
It may be uncomfortable thinking, but, again, unless you literally never take even the smallest risk in the pursuit of other goals, you are already thinking this way. You just haven't lifted it up to the conscious level yet.
No one is asking for infinite value. A cursory glance at causes of death rates in USA reveals that far too many people are dying in automobile collisions. There is nothing about our world that requires that level of carnage. Future generations will find our customs ghastly.
As in the famous Churchhill quote, once you agree it's not infinite, now we're just dickering about price.
I'd say you're almost right about nobody asking for infinite value, but I'd say it's more like nobody who has pulled this up to the conscious level is asking for infinite value. People who have not examined the belief are quite prone to speaking as if life's value is infinite... but their own actions inevitably belie that claim. Once examined, it becomes rationally obvious that life is not infinitely valuable (including your own), but, well, if humans automatically accepted and believed all rational things they examine without emotional consequence the world would be a very different place.
Agreed, your parent post was strawmanning. Is there a name for this second-order sort of meta-strawmanning, in which we imagine people's unconscious inclinations, rather than merely imagining their arguments?
The United States government led by the Obama administration came up with values from 6-9 million dollars when weighing marginal costs of safety regulations.
>It is possible to determine the value placed on life, I believe there are studies that show the value is more stable than you might think, and balance things appropriately.
For evaluating safety regulations relative to the cost of inplementation, NHTSA values the risk of loss of human life in relation to the market value of risk reducing products, and the safety they provide.
They extrapolate from the take rate of airbags and their cost and effectivity, to how much value the average American places on their own life. IIRC on the order of $5 million.
FYI, juries do not look kindly on companies that implement this in liability suits. The data is that if a corporation writes down a $-figure for a (statistical) human life, it anchors punitive fines at a higher level.
Well, you do waste minutes of peoples lives.
Let's see: 100 mio people driving 250 days/year, losing 10 min each way (so 20/day). That's about 12k lives of 80 years. It's actually worse, because you are wasting "awake time", so add 30%. It seems America isn't /that/ far of from the optimum. Maybe better driver education or better roads would be more effective?
The real issue with driving slower is enforcement. Enough people don't take into account the speed limit that changing the speed limit without changing the roads leads to unsafe mixed speeds.
Universally adhered to lower speed limits in urban environments would be great.
Certainty of enforcement. People are careful to obey a rule punished 100% of the time with a $1 fine. They brush off a 10^-5 probability of a $100,000 loss by thinking "It won't happen to me."
Correct. I often walk down a road with a 20mph 'limit' where most cars are doing around 40 - and some appear to be doing more like 50. There's simply no economically viable way to enforce it, so it will continue like this until there have been a couple of fatalities.
Not a chance. And that is a good thing. This knee jerk towards "lets just monitor everyone, everywhere and automate the law" is antithetical to a free society. Most people know that, which is why speed camera votes always send that company (RedFlex or whoever) packing.
I don't know about the US, but where I live speed camera are relatively large bright colored boxes with reflective stripes on the side of the road, with mandatory "speed camera ahead" warnings.
Most of them are empty but people unfamliar with the place will usually slow down.
The laws are state and local. In AZ it's a city or township, then the people put it on the ballot and it gets shut down. Tucson voted 65% no cameras, and later we got a state wide ban on highways, so it's a still a work in progress. The tickets are civil law, so you can throw it out, frame it, or make a coffee table book if you get enough:)
You can lower speeds quite drastically with better street design, no enforcement needed. Make the road narrower and curvier instead of wide open and straight. You can even add bumps.
I suppose you're suggesting there's a distinction between someone losing x hours of life due to travel time vs. someone being killed and losing y hours of life. I'm sure you can see why someone attempting to create a reasonable policy might avoid making that distinction.
I thought you were asking about "the cost of driving slower"? I'm perfectly serious in my answer. Any transportation goal (with the possible exception of ambulance service?) that may be accomplished at high speed, also can be accomplished at lower speed, with sufficient planning.
But what about an even lower speed? If 15 mph is good, then 5 mph is better. And if 5 mph is better, 1 mph is superior once more.
I think we can agree there is a point where slow becomes too slow and the 'sufficient planning' becomes an unreasonable burden. So given we aren't operating off the notion that slower is inherently better, then there is some equation giving us our optimal point. What if that point is 45 mph instead of 15 mph?
In short, how do we argue that 15 mph is better than 45 mph that can't also be applied to speeds lower than 15 mph?
It's easy - you have diminishing improvements in pedestrian survival rates. 40MPH+ is associated with a fatality rate of over 50%, whereas you get to 30MPH and you have 7%, and 20MPH is essentially zero: https://nacto.org/docs/usdg/relationship_between_speed_risk_...
Even if it is close to zero, how do we decide if the lives saved from going from a .1% fatality rate to a .09% fatality rate is worth the speed reduction or not?
jerf addressed this above. What you're saying isn't accurate. Doing things more quickly avoids wasting hours of life. That's a benefit. The cost is measured in hours of life of people killed and injured as a result of doing things at a chosen speed.
What activity are you talking about, that is feasible at 40mph in an urban environment but not at e.g. 25mph? Can you not imagine a different way of conducting that activity?
There is a fundamental inequity between the operator of dangerous equipment comparing hours and years of life, and the pedestrian who suffers the consequence of that comparison. The USA auto industry is built on this inequity, which is why no one ever talks about it.
Many people meet friends and make deliveries e.g. via bicycle. Those motorized vehicles that are set aside specifically for deliveries often travel more slowly than other motorized vehicles.
But I shouldn't pick nits; you were speaking in generalities! So when I said "any transportation goal" and you disagreed, you hadn't actually thought of a particular exception to my universal statement. And you still haven't thought of one. Are your contributions to this discussion offered in good faith?
1. I want to visit a friend. He lives an hour away by car. New speed limit changes it to two hours. I lose an hour of life in the car.
2. Auto plant needs radiators. Truck delivering them takes longer to get them there. Costs $x more. Car costs more. Car buyer has to work longer to buy car. Car buyer wastes y hours of life.
Or maybe you don't visit your friend so often. Or you decide that 90 minutes on the train is better than driving, or maybe your friend gets tired of making a 2 hour trip to the city, so he moves closer.
There are lots of alternatives that don't involve you spending more time driving.
While it's true that goods will cost more to transport if it takes longer, that higher charge is amortized across many products in the truck, so is a very small portion of the finished product.
So if a radiator fits in a box 16x24x6" or 1.3ft^3 and a 40ft truck holds 2400 ft^3 (subtract 20% since it won't be a perfect fix, so 2000 ft^3, so you can fit 1500 of them in the truck.
If a truck+driver costs $100/hour, that means each radiator will cost 13 cents more.
Or, another way at looking at it -- all of the parts that make up a car aren't going to be bigger than a car (sure, some space is lost to packaging, but there's a lot of empty space in a car), and 6 - 10 cars can fit on a car carrier truck, so each car will end up costing around $25 more.
Though since we're talking about urban speed limits, and there aren't many urban car manufacturers, slow urban speed limits won't affect the price of cars.
I suppose this subthread is complete, because you have now completely agreed with my original statement: you'll have to leave earlier for your trip to visit your friend, and delivery trucks will have to allocate more time (routes, trucks, drivers, etc.) for their deliveries. Alternatively, freight trucks might make fewer mostly-empty trips. Note that these two examples clearly match the characterization I provided: both may be accomplished at lower speed, with sufficient planning. This will be the "cost" of safe driving.
>Indeed. This is why many cities are reducing speed limits.
In fact, self-driving cars may actually improve the situation if cars actually start complying with speed limits en masse.
The vast majority of people just go however fast they feel comfortable (considering conditions, etc) regardless of the speed limit.
Mixed traffic speeds decrease safety.
Raising speed limits so that you don't have the % of people who comply with the letter of the law traveling slower than the people who go however fast they're comfortable usually improves safety.
Unless your goal is to increase ticket revenue or appease the "think of the children crowd" there's no point to lowering speed limits. It doesn't do much to affect traffic speed. To do that you have to modify the road or do something to change the traffic flow.
Self driving cars will improve safety because they'll result in political pressure to raise speed limits to match reality and they'll make dynamic speed limits more practical.
Sure, but city streets are already mixed traffic. There are pedestrians, bikes, vehicles parking or turning, etc. It's not reasonable to raise the limit to what people want to drive and just ignore all the other users of the street.
Also, the optical narrowing mentioned in a sibling comment is quite effective. They've done that on a few streets near me via things like sidewalk bulb-outs at intersections, and swapping the parking lane & bike lane (so it goes curb-bike-parking-drive, rather than curb-parking-bike-drive). Everyone drives more slowly on those streets now - myself included.
It does work when the roads are designed properly. No, posting a random speed sign isn't going to slow down traffic. But speed bumps, chicanes, turns, smaller lanes, etc. will naturally slow down traffic, making it impossible to drive dangerously fast.
"Mixed traffic speeds" is a concept for 4-lane highways, not 1 or 2 lane city streets. It would not take many law abiding vehicles to bring a one or two lane road down to the speed limit.
Exactly. That is why we should ban all cars anywhere there is people, and they should be limited to highways. Because safety is most important, right? Right???
> Unless your goal is to increase ticket revenue or appease the "think of the children crowd" there's no point to lowering speed limits. It doesn't do much to affect traffic speed. To do that you have to modify the road or do something to change the traffic flow.
It’s very simple, put speed cameras on every corner, and fine in terms of day wages. E.g., one week of your income as fine for going x% above.
Several countries are doing parts of this already, or moving towards it.
Apologies for going off topic here, but I'm curious about this. I've tested every car I've ever owned and all of the recent cars with all-round disc brakes have outperformed this statistic, but I've never been able to get agreement from other people (unless I demonstrate it to them in person).
I'm talking about optimal conditions here, wet roads would change things obviously but each of these cars was able to stop within it's own car length (around 15 feet) from 30mph, simply by stamping on the brake pedal with maximum force, triggering the ABS until the car stops:
2001 Nissan Primera SE
2003 BMW 325i Touring (E46)
2007 Peugeot 307 1.6 S
2011 Ford S-Max
I can't work out how any modern car, even in the wet, could need 45 feet to stop. In case it's not obvious, this is only considering mechanical stopping distance, human reaction time (or indeed computer reaction time which is the main topic here) would extend this distance, but the usual 45 feet from 30mph statistic doesn't include reaction time either.
I knew I'd get called out for not including sources. Those figures are from published sources, and do not include decision time. I'd imagine that these sources are for "average" roads and "average" cars
Car and Driver did a test with sports cars and profesional drivers and came up with 142 - 155 ft from 70mph, while my first reference quotes 245 ft (around 40% less, so extrapolating, their stopping distance from 35mph would be around 20 feet).
The average car on the road is not a sports car with performance tires and is not stopping on a clean, dry track. So I don't think it's a stretch to assume that an average car on average roads with tires optimized for tread life would be 40% worse than a $100K sports car with $400 tires that are optimized for grip rather than lifetime.
In addition, some cars such as the Nissan Leaf have a feature that locks the brakes at full power when there is a sudden control shift from accelerator to brakes, meaning that if you stomp on the brakes and then reduce pressure, the car will continue to brake at maximum power. This was done for two reasons: one, people hesitating in emergency situations, and two, people being taught to pump brakes, which increases braking distance in cars with ABS.
I learned about this feature when reading car forums for my car and finding threads from people who were rear-ended when they accidentally triggered this feature by slamming on the brakes when they didn't intend to come to a complete stop.
> In addition, some cars such as the Nissan Leaf have a feature that locks the brakes at full power when there is a sudden control shift from accelerator to brakes, meaning that if you stomp on the brakes and then reduce pressure, the car will continue to brake at maximum power.
Which is utterly stupid. Braking is the natural reflex, but not always the right one. I've been in more than one close call (think left turn on incoming traffic) where the correct response was not to floor the brake, but floor the gas.
> people being taught to pump brakes, which increases braking distance in cars with ABS.
Which is a mechanical turk version of what the ABS is doing under the hood.
> I'm talking about optimal conditions here, wet roads would change things obviously but each of these cars was able to stop within it's own car length (around 15 feet) from 30mph, simply by stamping on the brake pedal with maximum force, triggering the ABS until the car stops
How did you measure that? Because plugging these figures into a uniform acceleration calculator, 50km/h to 0 in 4.47m requires a deceleration of 2.2g but "Analysis of emergency braking of a vehicle"[0] experimentally measured very best case deceleration as barely scraping 1g (with ABS at 80km/h, significantly lower at lower speeds or without ABS).
So, there's a performance envelope expected. Sure, someone can bungee jump off an overpass and not be avoidable. :)
But they should be willing to walk in front of it in an in-spec performance regime. There's some really good Volvo commercials along that line, with engineers standing in front of a truck.
Unlike humans who have limited vision, self-driving cars are generally able to observe all obstacles in all directions and compute, in real-time, the probability of a collision.
If a car can't observe any potential hazards that might impact it using different threat models it should drive more slowly. Blowing down a narrow street with parked cars on both sides at precisely the speed limit is not a good plan.
You could do that, but how far do you take it? Do you program a car to slow to 10mph every time it passes a parked delivery van just in case? Would people find that acceptable?
Yes? If self driving is being hailed as being safer, it, you know, should be. If that means doing all the boring stuff I would not bother to, so be it. How else will they be safer unless by ignoring our driving biases?
Phoenix transportation infrastructure is notoriously bad at handling pedestrians and bicycles because so few people are going to be out biking in 120F summers. There's a knock off effect of exclusively designing a city around middle class car and house types of folks. It's why I left after 20 years in Phoenix and Tempe.
If self driving cars are limited to speeds that allow them to stop within their lidar max range is that too slow? Humans don't have the pinpoint accuracy of lidar but our visual algorithms are very flexible and robust and also have very strong confidence signals e.g driving more carefully in dark rain.
Cameras are not accurate enough though, their dynamic range being terrible. Wonder how humans would fare if forced to wear goggles that approximated a lidar sensors information.
The advantage self-drivers have is in
1. minimizing distraction / optimizing perception
2. minimizing reaction time.
Theoretically self-drivers will always see everything that is relevant, unlike a human driver. And theoretically a robot-driver will always react more quickly than even a hyper-attentive human driver, who has to move meat in order to apply the brake.
But is that the actual situation we're talking about? Or are we actually talking about a situation where the person may have been jaywalking but would have had a reasonable expectation that a human driver would stop? I walk a decent distance to work every day and I don't think anyone totally adheres to the lights and crosswalks (not least because if you do you will be running into the road just as everyone races to make a right turn into the same crosswalk you're in).
Then we should at least learn their capabilities by throwing jumping dummies at them. Call it the new dummy testing. It's the least we can do. Did Travis bro do this when he set the plan in motion?
Maybe not in the U.S., but in Norway, as part of getting the driver's license, you'll have to take an ice driving course, where, amongst other things, a dummy is swung at your car while driving on an oiled lane in 30 mph. (It is practically impossible to steer away from the dummy, which is the meaning of the exercise; to realize the folly of driving too fast on icy roads)
Because it's assumed human drivers will at least have a desire to stop. If a machine isn't properly programmed, it will plow right through a crowd and never look back.
Braking distance (without including any decision time) for a 15mph car is 11 ft, for a 30mph is 45 ft. Self driving cars won't change these limits. (well, they may be a little better than humans at maximizing braking power through threshold braking on all 4 wheels, but it won't be dramatically different)
So even with perfect reaction times, it will still be possible for a self-driving car to hit a human who enters its path unexpectedly.