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DeepTraffic is a gamified simulation of typical highway traffic (mit.edu)
180 points by kiril-me on Jan 18, 2017 | hide | past | web | favorite | 90 comments



Why is everybody driving in random lanes? You should only go into the outer lanes to overtake traffic, and then move back in once you've passed. It's not just the law, it's a good idea...

EDIT: And for anyone looking for more info, this seems to be a more useful page: http://selfdrivingcars.mit.edu/deeptraffic/


Also, they all seem to be changing objectives and speed at random. In my experience (European highways), it's usually pretty easy to categorize other cars into different patterns of behaviour, such as "wants to move as fast as possible", "wants to save gas by staying below the speed limit, preferrably right behind a truck" or "trying to maintain preferred speed, changing lanes as needed". Also, most cars will act in a fairly safe and rational way: avoid tailgating, signal before lane changes, maintain speed and lane unless there is a good reason to change, try to stay clear of other cars which they find unsafe. It's an interesting system, actually, and one which is very much based upon experience and intuition.

By contract, the cars in the simulation seem to change lanes and velocities all willy nilly. All of them flip my bozo bit and my intuitive reaction would be to position myself to take the closest possible exit ...


have you driven on a UK motorway recently?

tailgating? yep cutting into traffic? yep randomly slowing down and speeding up? yep


As far as I know, it is common in Europe to only overtake on the outer lanes. In the US however, there are no such rules.

It does seem like a good idea to me.


The law exists in the US, but nobody bothers to follow it from my experience driving there. People just seem to use the other lanes as more road.


It's pretty well followed on the highway in low traffic conditions. Trucks and such will stay right. During heavy traffic nobody gives a flying fuck though, and I've never heard of the law being enforced once if it wasn't a charge being tacked onto something else like reckless driving


On top of that, there will always be "sections" of the road where traffic reliably grinds to a halt. So people keep switching back and forth to avoid those areas.


The US does not have one set of traffic laws for all states.


Most states follow the Uniform Vehicle Code on this issue

http://jalopnik.com/5501615/left-lane-passing-laws-a-state-b...

(and among those that don't 1/2 of them still have laws about obstructing traffic)


The issue mentioned in your linked article is different from what's mentioned up thread. The article deals with "what is the role of the very left lane". Upthread it's about using non-outer lanes (inner lanes) as the passing lane, which implies passing on the right. The UVC specifically allows passing on the right on a paved road with 2, or more, lanes (see 11-304(a)(2))


jstanley at the top of the thread is clearly talking about the same thing as my article, keeping right except when passing.

You should only go into the outer lanes to overtake traffic, and then move back in once you've passed. It's not just the law, it's a good idea...

That's not about passing on the right.


The outer lanes are the left and right lanes. Which implies that, given 3 lanes, someone is passing on the right.

At a base level, given more than 2 lanes, there is a difference between "stay out of the left lane unless passing", and "stay out of the left and right lanes unless passing", as it gives drivers twice as many options for passing.


I would have said that in USA the "outer lane" is the rightmost lane, since it's the one that forms the edge of the highway. Likewise, in UK it would be the leftmost lane. The inner lanes are the ones adjacent to the median in a divided highway. I think OP simply misspoke, because everyone knows one is supposed to pass using the inner lanes.


The UK Highway Code stopped talking of inside and outside lanes, because it's confusing. They now talk about left hand lane and right hand land.

https://www.gov.uk/guidance/the-highway-code/motorways-253-t...

> Rule 264 You should always drive in the left-hand lane when the road ahead is clear. If you are overtaking a number of slower-moving vehicles, you should return to the left-hand lane as soon as you are safely past. Slow-moving or speed-restricted vehicles should always remain in the left-hand lane of the carriageway unless overtaking. You MUST NOT drive on the hard shoulder except in an emergency or if directed to do so by the police, traffic officers in uniform or by signs.


Pretty sure that by inside lane they mean the main traffic lane.

http://dictionary.cambridge.org/us/dictionary/english/inside...

(I made that assumption before noting the .uks in their profile...)


What I've never understood about this idea is that it suggests that speeding must not be illegal in that passing lane. But that's not true. So then how does a law for a passing lane work?


Speeding is still illegal, but so is creating a traffic hazard by impeding drivers who wish to speed. The overall principle is that unsafe behavior on the road is prohibited. Full stop. It doesn't matter that your behavior is unsafe only because other people's behavior is also unsafe and prohibited.

There's usually a clause in traffic ordinances that state something along the lines of "regardless of any of the other laws here, drivers have a duty to avoid collisions if they can."


Basically, what speed other people drive is not of anyone business except the police. If you are not overtaking, stay right and let them take the risk.


I'm not sure where you get the suggestion that there is no speed limit in the passing lane. We drive on the right so the safest place to pass is on the left where the driver is. If everyone stays right as much as possible and faster traffic (this does not imply speeding) can move left to pass then traffic flows smoothly.

Where are you getting the impression that speeding is allowed anywhere?


> Where are you getting the impression that speeding is allowed anywhere?

One reason is that in many places in the US, the normal traffic speed exceeds the legal posted limit by 5-15 miles per hour. If the law requires a driver travelling at the legal speed limit to stay out of the "passing lane" so that other drivers can pass, this would imply that the law condones speeding, since only a driver moving faster than the legal speed limit can make use of that lane. If the law was not intended to encourage exceeding the speed limit, it likely would have been written as something like "any driver moving less the legal speed limit must avoid the passing lane".

Another reason is that some US states make exceptions to the normal speed limit when passing another vehicle on a two lane road: http://blog.seattlepi.com/seattle911/2014/10/10/can-i-speed-..., http://www.mlive.com/news/index.ssf/2012/03/traffic_talk_com.... While one could argue that it's not "speeding" if it's not illegal, it's not unreasonable to interpret such laws as "allowing speeding" to pass.


> If the law requires a driver travelling at the legal speed limit to stay out of the "passing lane" so that other drivers can pass, this would imply that the law condones speeding, since only a driver moving faster than the legal speed limit can make use of that lane.

That's not how it works. The law is "stay right except to pass". This is true regardless of speed. Speeding is still illegal in any lane. The "stay right" rule is about not obstructing the flow of traffic, it has nothing to do with the posted speed limit.

e: To clarify many people drive below the speed limit, in this case it is possible to pass them in a lane to the left without exceeding the speed limit.


> The "stay right" rule is about not obstructing the flow of traffic

I agree, but the crux is whether one is prohibited from obstructing just the legal flow of traffic, or from obstructing any flow of traffic. Different states define this differently. Indiana, for example, recently reworded their law to require you to allow any one to pass you even if they would be breaking the law to do so: http://www.nwitimes.com/news/local/govt-and-politics/new-ind.... While this doesn't make speeding legal, it strongly implies that drivers who wish to illegally exceed the speed limit in Indiana have a right to do so.


>the crux is whether one is prohibited from obstructing just the legal flow of traffic, or from obstructing any flow of traffic.

Pretty much all the laws don't say "but if you're driving the speed limit, you can stay in the left lane". It's all more like "keep right except to pass slower traffic". It's pretty clear.

>While this doesn't make speeding legal, it strongly implies that drivers who wish to illegally exceed the speed limit in Indiana have a right to do so.

No, it doesn't. It says that both speeding and blocking speeders by loitering in the passing lane are both traffic violations. If you want to drive legally, stay under the speed limit and out of the left-most lane (except when necessary to do so for exiting, passing, making way for emergency vehicles, etc).

It's not that complicated.


> It's all more like "keep left except to pass slower traffic". It's pretty clear.

Forgive me if you are in a left driving country but since this is a conversation about US State traffic laws I think you meant keep right except to pass.


yeah, thanks, I accidentally edited the phrasing from something like "don't go in the left lane" to "keep left".


I disagree that the Indiana law implies a right to speed, it just says that traffic should not be impeded. If you are going 65mph in a 65mph zone on a two lane road and someone comes up behind you at 80mph and you move over to pass as required by that law it's still entirely possible that they will be pulled over after they pass you.

The law is about reducing the hazards on the road. Impeding traffic flow is extremely dangerous, more so than most people seem to realize [2]. These laws also apply in cases where the passed vehicle is traveling below the speed limit.

The "stay right" rule is about not obstructing traffic because doing so is very dangerous. If that traffic is speeding then yes, they are also technically in the wrong but it is important to also stay right and not create an even more hazardous situation.

This also means the "cruise control pass" where one car slowly overtakes another is also illegal if it is delaying anyone else from passing.

Washington State has a similar law [1] as does Idaho I believe.

[1]: http://app.leg.wa.gov/rcw/default.aspx?cite=46.61.427

[2]: https://www.youtube.com/watch?v=4oqfodY2Lz0


Responding to a comment that was deleted while I typed (sorry for any misformatting; copy/paste/edit is kind of difficult in the microscopic text box on a phone):

Retric 6 minutes ago | parent | flag | favorite | on: DeepTraffic is a gamified simulation of typical hi...

It's much safer for a few semi's to block all lanes while going the speed limit than to let people pass at 80+MPH. So, moving to the right lane has little to do with safety just enabling speeding. In heavy traffic police will sometimes do this at below highway speeds which can create a huge net benefit.

Further, lane changes are dangerous and should be minimized.

It's hardly safe if the natural speed of traffic behind the semis is x+5 and the semis are going x. Then you have a constantly growing number of cars trying to fit in the same amount of space, and density seems way more dangerous than speed.

I don't understand why some drivers feel the need to control every other driver behind them. As other commenters have said, it is more dangerous (and less efficient) to create a backup than to just let faster traffic pass, regardless of the numbers printed on the signs.

It is not your job as a driver to police other drivers. Maybe your bald all seasons on your cheap sedan can only go 55 in a 70 in the rain, but that other car has rain tires and traction control that could handle 110, so they are safe at 70 in a 70. Preventing them from passing is unsafe and deeply impolite.


I really believe we should have mandatory driver testing on a regular basis. Say every 5 years for a skill test and a written test every year. Written test could be through the mail and it could be funded by increased penalties on speeding and impeding traffic flow.

I got my drivers license in Idaho then moved to Seattle years later. Washington took one look at my Idaho license and handed me a Washington license. There were no questions asked about traffic laws or anything.

This city has grown substantially in the last 10 years and it's starting to show in the traffic. We have big backups but we aren't at capacity, drivers are just very inefficient in their habits. Last year there was a push from the DOT to encourage zipper merging to more efficiently use our roads. I try to follow that advice but drivers aggressively prevent the merge at the merge point, probably because it seems to them like I am "cutting" in line.

I think we could make big improvements just with some education. Self-driving cars will help but making people better (even a little bit) will help. And if human drivers follow the rules more reliably that has to make the self-driving car's job easier during the long transition from all human to all AI controlled.


> Impeding traffic flow is extremely dangerous, more so than most people seem to realize

Sure, if we accept the current reality that many drivers drive faster than the law allows, it likely improves overall public safety to allow them to do so unimpeded. My preference would be that we either enforce the existing laws, or change the laws to match the norm. But although there are many situations where the chance of immediate harm would be reduced by avoiding confrontation, I think it's rare that citizens are legally required to accommodate law breakers.

For example, while it may reduce the risk of bodily injury to peacefully turn your keys over to a carjacker, it's unlikely that we would criminalize refusal. I presume this is because society tolerates (accepts, condones) speeding in a way that it does not tolerate carjacking. At the least, I think it implies that laws are divided into (at least) two classes, laws that individuals must allow others to break, and those that they are allowed (or encouraged) to attempt enforcement.

Can you give other examples of illegal activities where third parties are required to take positive action to allow? And where there isn't widely considered to be a "right" to break that law? I'm sure they exist, but I'm not coming up with them.


Impeding the flow of traffic is dangerous regardless of the presence of speeders, it is also against the rules. If you aren't following the "stay right" rule then you are as wrong as a speeder. You can't pick and choose what rules you want to obey.

> At the least, I think it implies that laws are divided into (at least) two classes, laws that individuals must allow others to break, and those that they are allowed (or encouraged) to attempt enforcement.

Maybe I misunderstand what you mean but I'm not aware of any situation where private citizens are encouraged to enforce the law. That's a recipe for disaster and is where road rage is born. Should I drive around and tailgate everyone in the left lane to teach them to drive on the right? What's the difference?

e: The "drive right" rule is not about allowing speeders, it is about not impeding the flow of traffic. It's similar to "yield to the right", the rules of the road are designed to allow all of us to use a shared resource efficiently.


It's likely that we agree on real-world practice: one should allow vehicles to safely pass regardless of the legality of their speed, and harassing someone who is driving in the wrong lane is to be avoided. I drive as politely as I can, both for my own safety and that of others.

That said, I am philosophically troubled by a law that legally requires me to take a positive action that benefits those who choose to ignore the law. I'm not sure what the parallel would be to your "yield to the right" example --- perhaps requiring that the driver with the legal right of way check first that no one has chosen to ignore the yield sign?

I would be interested in better parallel examples where positive action is mandated to improve public safety in the event that another party is breaking the law. My guess is that degree of comfort with similar laws show a strong urban/rural split, based on the degree to which "leave the policing to the police" is feasible.

(note that I'm not questioning the general principal of "slow traffic keep right", only the corner case where all traffic is already moving at the legal speed limit)


I can not provide parallel examples but I disagree with your premise that you are obligated to stay right to enable others to break the law. Even if you are the only car on the road you still must drive in the right lane unless passing.

The law says to stay right regardless of speed so there is no corner case based on traffic moving at the legal speed limit. Your obligation to stay right exists at all speeds.

The purpose of the law is to improve safety by enabling smooth traffic flow and creating a predictable environment on the road. This is the parallel with "yield to the right". Communication between drivers is difficult so we have a set of rules to guide us in situations where the next action may otherwise be unclear.

If two people meet in a hallway they can look at each other and say "excuse me" or "go ahead". This is not possible on the road. In the same way I can walk up behind someone on the sidewalk and say "excuse me" and walk around them. In a car this is not possible so we agree in advance (or rather, we are told by the authorities) what to do to avoid the situation and how to reconcile it.

In some jurisdictions the purpose of the left lane is explicitly passing, you have no right to drive there unless you are passing someone else. In this case your obligation to stay right has nothing to do with the existence of a speeder or even your rate of speed.

I am not defending speeding because it does increase risk and reduce safety on the road but it becomes much more dangerous when other drivers are also not following the rules. Breaking the speed limit while someone else violates the lane occupancy laws creates a compounding risk for everyone on the road. This is why we have rules against both.

I would turn your request for parallel examples around and ask you for examples of a situation where it is ok to break the law to prevent someone else from doing the same. How do you justify such an action and is there a calculation as to how far to go? Is it ok to jaywalk to stop a robbery? Is it ok to murder someone to prevent jaywalking? When is vigilantism justified?


I disagree with your premise that you are obligated to stay right to enable others to break the law.

My premise is actually a little different, which is that a keep-right law without an exclusion for vehicles travelling the speed limit implicitly condones speeding. I'm questioning the intent of the lawmakers, not suggesting that the state laws should not be followed as they currently exist.

The law says to stay right regardless of speed so there is no corner case based on traffic moving at the legal speed limit.

Well, except (as best as I can tell) for Alaska, Arkansas, Maryland, Michigan, North Carolina, Ohio, and South Dakota, plus a couple more that make an exception if you are travelling faster than traffic flow: http://www.mit.edu/~jfc/right.html.

Interestingly, though, it looks like the current trend is for states to move away from this approach that I feel is more logical, and switch to a blanket "keep right except to pass" that you seem to prefer. This would suggest that my concerns are becoming less widely shared by others.

I would turn your request for parallel examples around and ask you for examples of a situation where it is ok to break the law to prevent someone else from doing the same.

This is a question that does trouble me, but I'll start by reiterating that I'm not encouraging people to ignore this law. Rather, I'm more interested in whether laws of this sort have an overall positive effect for society.

But answering the question, I think nonviolent actions such as taking someone's car keys to prevent them from driving while intoxicated might be justifiable. I think there are cases where releasing classified documents showing illegal government activity is morally justifiable. And there are times when I'd approve of stopping a violent crime in progress using otherwise illegal force against the perpetrator.

Is it ok to jaywalk to stop a robbery?

Yes, although I guess you'd have to weigh the chance that the jaywalking would endanger others.

Is it ok to murder someone to prevent jaywalking?

Apart from contrived cases involving extremely fat pedestrians and runaway trolley cars, I have trouble coming up with a case where this would be appropriate.

How do you justify such an action and is there a calculation as to how far to go?

Personally, I don't know, but I read this article earlier today and thought it had a good overview of some different societal approaches to the problem: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=2718211.

It points out that common law systems (most of the US) typically have few requirements for citizens to prevent or report third party crimes, while citizens in civil law systems (some of Europe) often have a greater legal obligation to do so. Generally this obligation is satisfied by reporting to the police, but in some jurisdictions (Israel) there is a further legal obligation "to use all reasonable means to prevent the commission" of any felony.


Here's a nice video that explains the concept quite well I think: https://www.youtube.com/watch?v=4oqfodY2Lz0 (Title: Why you shouldn't drive slowly in the left lane)


There's an interesting British thing where lots of people are militant about lane positioning to the point of recklessness. I know otherwise down to earth people who absolutely loss it when there's someone in the middle lane on a motorway. I have friends who will pull close behind the offending vehicle, flash their lights, beep their horn and yell - which is obviously far more dangerous than the original offence. This is in cases where there's a totally empty "fast" lane further to the right. Many drivers almost feel entitled to not have someone in front of them in the middle lane.

I get the argument for staying over to the left (in the UK). I'm not convinced that it's 100% rational though.

Picture a normal scenario with 3 lanes and on/off ramps coming in from the left.

With light traffic, all vehicles can keep to the left, over taking can happen in the middle lane and there's space for vehicles joining via the on-ramp. Fine.

With really heavy traffic, you normally end up with 3 lanes of traffic moving at increasing speed to the right and all the lanes are utilised. Everyone seems happy. Fine.

What happens with the murky space in between? If you try to stack everyone in the left lane they need to keep making space for people joining from the ramps. Also, some people will be moving faster than those in the far left, so they're effectively overtaking, but then where do you draw the line where they have to pull back to the left again (only to move out to overtake in another minute)? You could say that the moment there's any space to the left you move into it, but you just end up with lots more lane changes - which, at some point, becomes more dangerous than everyone just staying in the same lane.

There's a balance to strike between changing to satisfy the rule and staying the course to decrease the amount of changing. For different people that line is in different places and for a lot of people I know who grew up in the UK, if they place your behaviour on the wrong side of that (arbitrary) line, there will be hell to pay.

As a once foreigner it's all quite interesting.


observations from austria (remember we have the steering wheel on the right side ... so, the left).

the law on the autobahn/multi-lane streets is: change to a lane on the left (a faster lane) only to overtake (except for special conditions, i.e. traffic jams/very slow moving).

mostly south of vienna, the system is different though. due to the high amount of traffic from eastern neighboring states, with different rules and different speed limits (austrias autobahn speed limit is 130km/h, while in the east it's sometimes 120km/h, i'd guess), it's usually:

* right lane (slowest): trucks and slow moving vehicles ~80-100km/h

* middle lane: normal traffic, depending on weather ~110-120km/h (with sometimes up to 130-140km/h if traffic permits, usually not for long though)

* left lane (fastest): traffic going faster (130km/h+)

you choose the lane appropriate for your speed. overtaking strictly on the left.

this is, strictly speaking, not legal. if the slower lane is free you have to change, even if you're going top speed.

in the beginning i've been complaining about people not observing the local laws, but nowadays i have to admit that i think the eastern system works better.


Looks like relatively normal behavior for a 7 lane road for either USA or Europe.

Highways with THAT many lanes typically have exits on both the right and left side. People will typically be on whichever side their exit is going to be on.


In Europe exits on the left of the motorway are quite rare (excluding countries that drive on the left).


Driving in the UK is sheer hell. Most people drive in the middle lane regardless of whether they are overtaking or not. Go to the continent and it is pure bliss by comparison. Brits even mistakenly call the outer lane the 'fast' lane. It is actually the serious offense of 'Driving Without Due Care And Attention' but UK transport police are worse than useless. On education - there is no test of motorway/highway skills for your driving license! Also, many UK people even deliberately obstruct other road users. The law states that you _can_ undertake. It is detailed in what is known as the Highway Code. Undertaking is allowed in a one-way system eg. motorway provided the vehicle to your right is not overtaking e.g. maintaining a constant speed sitting in the damn lane like they own it making everybody else do their driving. I'll go now before rant mode fully kicks in....


And yet the UK has the third lowest crash rate in the world compared with population and the second lowest crash compared per distance driven.[0]

Also, your facts are wrong. You are required to practice on your highway skills and you will almost certainly go on a highway (if location permits) during your test. I'm almost happy we don't train our newer drivers on the motorway, honestly, I'm not sure I would trust them not to mess up even with an instructor joining them. We do have debates about whether to let newer drivers go on the motorway [1], but people bring up the point that they're normally incredibly busy and a single mistake could kill 5+ cars travelling at 70mph.

Also, you say we can't call the outer lane the "fast" lane? It is fast when compared to the other lanes, but this doesn't mean we need to drive without care or attention! I think you don't understand that "fast" is a relative term and does not mean you can break the speed limit.

A couple of other points:

- You can't undertake normally, only in specific circumstances such as in queues or in separated traffic situations (like one-way traffic). You are NOT allowed to undertake on a motorway.

- "Many UK people even deliberately obstruct other road users" has never happened to me in my life but, I've heard others talk about doing it to others when they're not being considerate to others (for example when two lanes go to one, and a car thinks they can speed down the fast lane to overtake everyone and just bully their way into the left lane).

- "Pure bliss by comparison", really? Italy is notoriously bad at driving, Spain and other places also have similar problems with them. Generalising the entire continent to be perfect doesn't work.

[0] https://en.wikipedia.org/wiki/List_of_countries_by_traffic-r... [1] http://www.bbc.co.uk/news/uk-38464776


I think his issue with the word fast (and mine) is that collectively calling them "fast" lanes instead of "passing" lanes is part of the problem. Then you have incognizant drivers thinking "I drive fast, this lane must be for me"


>- "Pure bliss by comparison", really? Italy is notoriously bad at driving, Spain and other places also have similar problems with them. Generalising the entire continent to be perfect doesn't work.

Usually when I see people comparing the UK to continental Europe like that, they're really talking about northern Europe, and conveniently ignoring Spain and Italy.

It's like that here in the US: any time we say something positive about our country, we're usually ignoring the existence of the South.


> Most people drive in the middle lane regardless of whether they are overtaking or not.

This is not true. A small, highly annoying, minority drive in the middle lane regardless. Most people drive reasonably.

My least favourite thing is in these new 50mph limits on the motorway, where people will sit in the fast lane doing exactly 50, holding others up. They wouldn't do it on a regular section of motorway with a 70 limit, why do it in a 50?


>They wouldn't do it on a regular section of motorway with a 70 limit, why do it in a 50?

I would guess because 70mph is the default speed on a motorway, and the highest speed limit possible, and it's generally accepted that people often drive faster than that on motorways in the UK. Whereas 50mph is unusual and thus seems more intentional, and thus more likely to be enforced.


I'm fine with people driving at 50, I just think they shouldn't be doing it in the fast lane. They should get out of the way except when overtaking.


The 50mph limits are usually temporary and enforced by average speed cameras.

The number of people who blast through those sections well in excess of 50mph never ceases to amaze me.

I can only assume they don't understand how average speed cameras work.


I regularly drive through them at more than 50 and have never received a ticket from one. The cameras are either not operational or the enforced limit is higher than 50.

And my point was nothing to do with the speed camera. My point was that you have no right to sit in the fast lane holding other people up, regardless of what the speed limit is. Get out of the way if you're not overtaking.

EDIT: This isn't directed at you, just a general rant.


It depends on the state.

Some states do not permit undertaking.

Others do.


The law is the same in the US -- but, your comment is quite telling.


But are there rules that disallow overtaking on the right?


Strangely more people seem to know about this than about only using the left lanes to pass. I have seen several people get worked up about being passed on the right, to which my response is "why were you driving on the left"? They don't realize that the slower vehicle chooses the overtaking lane - whichever lane they aren't occupying. In my opinion it's down to the signage: "SLOWER TRAFFIC KEEP RIGHT". Nobody wants to think of themselves as slower. Should say "LEFT LANE FOR PASSING ONLY".


For most states, those rules generally don't apply when the passing is happening in a lane of travel. Instead, they refer to situations like using an exit-only lane to pass, trying to pass in a gap between parked cars, or passing on the shoulder.


In Utah, we can pass on the right as long as there are more than two lanes. If there are only two lanes, you are supposed to only pass on the left. As noted in other comments, this is state-based and I've never once seen it enforced.


In Europe fast traffic go left. If some one slow way it always overtaken on free lane.


|Why is everybody driving in random lanes?

Because that's closer to how humans drive. As infuriating as it is, midwest-USA traffic follows almost no rules about what the left lanes are for.


Varies by state too. Not every state requires people to keep right.


My particular pet peeve is being undertaken by fellow cyclists! It's not like I'm even going slowly!


Undertaken? How far out in the road are you riding? I've never undertaken a fellow cyclist in my life, out on the open road, and I can't think that I've ever seen it done.


Quite common on roundabouts or when parked cars are on my inside; I've seen too many people nearly killed by the sudden opening of a car door into their path. On roundabouts I try to take up the whole lane so drivers know what you are doing and don't assume you are turning off.

I could probably write a book about defensive cycling; the amount of times drivers would have turned into me if I wasn't predicting it is probably over 50... it's the most common way to be killed.


> Why is everybody driving in random lanes? You should only go into the outer lanes to overtake traffic

And if you need to exit the road. Or if you think you need to Soon (tm).

As someone else already put: in Europe you need to drive at the outer lanes (usually right, UK left lanes) if you're slow, and if you want to overtake traffic you move inward (usually left, UK right lanes) after which you should ASAP move back to the outer lane.

Its logical that people from MIT try to emulate US traffic or even Massachusetts traffic though.


That's a simplistic application of lane discipline principle to a 7-lane road. I'm sure you aren't advocating for everyone to drive in the rightmost except when overtaking. The question then becomes one of acceptable gradient. How much faster do I need to go to warrant the use of the lane to my left? Is there a quantum?

In America the accepted answers are "none" and "no". Also a 7-lane road is a terrible idea.


It's clearly a simulation of Western Australian traffic.


Come to Miami. There is zero lane discipline.


I've been recently driving in Australia and the behavior is spot on. Cars were overtaking on the left (inner sode of the road) as well.


As Australia drives on the opposite side to the USA - the general thing to do is slow cars move to the left and most overtaking is done in the "fast" / right lane(s).

In practise though, people go slow in the right lanes and are not considerate of other drives. Some even think they have the right to prevent others from speeding and deliberately do 5-10km/h under the limit.

The thing is, by not following the practise you cause other impatient drives (rightly or wrongly) to weave in and out of lanes passing on both sides which increases chances of an accident - due to the increase number of lane changes.


In states where it's legal to overtake on the left, there's no cultural obligation to stay in the leftmost unoccupied lane unless overtaking, and so cars end up scattered all over the lanes. Add in the government's myopic 30-year fixation on speed limits as the answer to any and all road trauma statistics (and their huge expenditure on propaganda to convince the general public) and you get self-righteous idiots doing 10-20km/h under the limit in the rightmost lanes smugly convincing themselves that they're "making the road safer" as road trains try weave around them.


> You should only go into the outer lanes to overtake traffic, and then move back in once you've passed.

Not in the US AFAIK (or does it vary by state?). My understanding and experience is that driving in the lane of your choice, and "undertaking" (overtaking on the inside) are both legal and common practice.


You are incorrect, but I can see why you would be confused, since so many people pick the left lane to go slow in. I think they imagine themselves to be some sort of force for good, slowing down all those evil speeders.

Here's a summary of the law, by state. http://www.mit.edu/~jfc/right.html


Huh, interesting. So it's a law that is neither obeyed nor enforced (in my limited experience).


I was able to get speeds of 71 MPH, now can anyone tell me exactly what I did because my approach was just to randomly change values, train and run.

I read the documentation and watched the first video and read all of the lecture slides but I haven't really grasped any of the concepts. Like, is 400 num_neurons a lot? Not a lot? Why would looking backward help at all? Why have that as a variable? It suggests to increase the train_iterations from 10000. Does that mean 15k, 100k, 1000k? Was that the point of the exercise, just to get comfortable with making changes and running simulations or should I have come away with a deeper understanding?

If anyone feels like they could teach me I'd be willing to pay $100 for a half hour of your time, skype or Cambridge/Boston if you are local.


I haven't played around with it much, but look at the layers of the network. First layer is the inputs which is pretty much one for each input square. If you want to be fairly optimal figure you need to look at 5 lanes total and at least 10 squares ahead (and maybe a few behind if you need to get out of a jam) so that's 50 inputs per frame but it is taking inputs from 4 frames so that's 200+ inputs in the first layer (plus 15 for the actions for the last 3 frames).

The output actions are 5 so that is the size of the output layer.

You can change the number of nodes in the middle layer but you can also cut-and-past that code to add additional layers.

I think you probably need at least two layers, the first to determine which lanes are clear and the second for figuring out how to maneuver into the desired lane.

With such a large network, training will take longer so stick with the default iterations until you feel like you need more fine tuning.


On second thought, I would say start with smaller models and work your way up. More complicated models take much longer to train, and keep training them until they plateau. Turn off the overlay and train on fast speed to get there faster.

Once you are satisfied with a model, change one thing and see how much of an improvement you get, but it is a time-consuming process. I have not fiddled with any of the "opt." options yet.


Do this course and you'll get a very good idea of what's happening, and it's free: https://www.coursera.org/learn/machine-learning


400 num_neurons is quite a lot, i trained a facial expression classifier in college a few years ago from images i got Online. That was for a basic feed forward classifier though, this is different.

The input layer was large but the hidden layer was only 12 neurons.

I'm still learning myself so i wouldn't be able to teach you. There are some great courses online.


400 units is very small. Today's image classification neural nets have hundreds of thousands of units (units is my preferred non-biological synonym for "neuron")


I will try to use units in future.

To be fair the net i created could only handle human faces correctly oriented and only at a single low resolution.


From the source, for those who are wondering what 'fc' or 'relu' mean:

          case 'fc': this.layers.push(new global.FullyConnLayer(def)); break;

          case 'lrn': this.layers.push(new global.LocalResponseNormalizationLayer(def)); break;

          case 'dropout': this.layers.push(new global.DropoutLayer(def)); break;

          case 'input': this.layers.push(new global.InputLayer(def)); break;

          case 'softmax': this.layers.push(new global.SoftmaxLayer(def)); break;

          case 'regression': this.layers.push(new global.RegressionLayer(def)); break;

          case 'conv': this.layers.push(new global.ConvLayer(def)); break;

          case 'pool': this.layers.push(new global.PoolLayer(def)); break;

          case 'relu': this.layers.push(new global.ReluLayer(def)); break;

          case 'sigmoid': this.layers.push(new global.SigmoidLayer(def)); break;

          case 'tanh': this.layers.push(new global.TanhLayer(def)); break;

          case 'maxout': this.layers.push(new global.MaxoutLayer(def)); break;

          case 'svm': this.layers.push(new global.SVMLayer(def)); break;


I wonder how simulations like this transfer to the real world. For example if you want to win in the real world you just start driving like a maniac. People will very quickly get out of dodge.

Spoilers: I tried to encode this idea by setting the inputs to be just tall enough to learn the safety system and wide enough to cover all lanes with no forward visibility. This learns an aggressive lane switching algorithm that lets you hit around ~70mph though not for the reason I thought. Also needed a few more hidden units/layers to make it work.


Yes, similar experiences here. It seems relatively easy to hit the 70mph mark but it gets tough past that.


For self-driving cars, I'd much rather your code control _all_ the cars, not just an individual.

Individualistic driving leads to worse overall performance for everyone. One of the things I'm most looking forward to in an all-code-controlled driving future is seeing efficient highway traffic moving fast and smoothly.

(And yes, clearly there's a long transition period where some cars are controlled while others are still human-driven.)


> I'd much rather your code control _all_ the cars, not just an individual.

That's not how the world works though. The only thing you can control is your own actions. Trying to control other people's actions is a recipe for failure.


> Trying to control other people's actions is a recipe for failure.

Trying to control other people’s actions is called a law.


> (And yes, clearly there's a long transition period

After that transition period, the automobile designers will start to optimize for a use case where the majority of the traffic is autonomous and agree on standards of how to align the different designs' goals.

It seems like that tipping point is so far away as to not make sense spending time on now. And I imagine even a century from now you will still see some vehicles driven by humans. There will always be exceptional transportation use cases, including cases where the autonomous vehicles forfeit control because of confusion or material defect (bad sensors, weather, etc).


Another advantage is that pedestrians can just walk wherever they want and cars will safely avoid them. Much more freedom for everyone.


Can someone help me understand - why is this in JS? [I'm asking seriously, not trying to start a language troll-war]. I ask because I'm designing a system that could use JS trained models (for wider company access) - yet I was unaware of tools that can run models at scale using JS (i've seen more in Python, R).


Because it's about teaching, not about getting the best possible performance. JS based stuff is easy to get working, because it's just "install chrome, go to <webpage>".


Fantastic I'm all about that. I wanted to make sure there hasn't been a leap in language tools that I missed. Thanks.


I'm guessing its so that it runs in the users browser (using their computing resources), rather than on MITs computers. If you get a lot of users, the difference could be very important.


8 lanes is easy

Try driving in 2 lanes with random people switching lanes in front of you, people randomly blocking your lane to turn, etc, also make sure you get into your destination on time


So, Is the idea that some autonomous cars could just drive around doing nothing other than setting the pace?




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