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Comment by LinuxBender | Hacker News Reader

Should traffic lights be abolished?

No. Phased out over time in some places maybe, not abolished. Implemented in some new developments, absolutely.

While roundabouts can work more efficiently they require the roads and traffic usage patterns to accommodate them. Additionally existing intersections designed for lights and putting in roundabouts would require cities in many cases to use eminent domain to acquire the land around them or to buy out land/properties from people. The excessive use of eminent domain would lead to endless legal battles that would deplete city budgets.

Some existing large intersections could be retrofitted for a roundabout and some small cities are in fact doing this. I've also witnessed this occurring in rural areas that have intersecting highways where the state already owns the land around the highways. This reduces brake dust, engine brake noise and keeps freight moving.

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The UK "mini-roundabout" does not take up additional space.

Roundabouts work best when the traffic is below a certain critical level; above that and you're still stuck for ages except with no automated system trying to bring "fairness". In some cases this can be solved by .. adding traffic lights to the roundabout.

> The UK "mini-roundabout" does not take up additional space.

There are plenty of small intersections with traffic lights that aren't any wider than two opposite lanes with no median and no shoulder, only big enough for two vehicles to pass in opposite directions. They would need to be expanded to put a circle of any size in the middle, especially if a big truck was expected to make it through safely.

A mini-roundabout is a centre circle painted (not curbed), plus the priority rules (give way to your right - would be your left in the US).

They don't take up any extra space, but they do probably require drivers to intuitively understand the concept and priorities before they can be introduced.

Here's a satellite view of a random one near me: https://goo.gl/maps/NJ2KpYdMP1reQA1u5

Its an upgrade of the American 4-way-stop with better defined priorities for entry.

That definitely takes up extra space. Notice all the room between the lanes. In many places in the US, you don't have even that. The intersection is literally only wide enough for two cars to go past each other, and _any_ amount of space taken up in the center means you need to widen the road.

Here's another one from Scotland. They don't have to take extra space. The version shown above only has extra space because they installed pedestrian islands - a nice touch but not required in many intersections.

Additionally, there is frequently extra space in the existing intersection. From parking lanes, shoulders, etc.

https://www.google.com/maps/@56.5902318,-3.3376212,3a,75y,34...

This is a much better example, thanks. That does indeed look like it doesn't really take up any more room -- the painted roundabout mostly seems to serve as a reminder of the yield order that people should take. In a way, its almost like a yield-controlled intersection here in the US. Those work relatively well as long as everyone follows the rules. In many places, this would just be inviting aggressive drivers to blow through intersections.

Exactly.

Worth noting this particular roundabout is in a small farming town on the edge of the highlands. Already slow speed road and low volume. But, shows that many 4-way stops within the US suburbs could easily be swapped with a roundabout during normal road repaving without much additional cost (yield signs to replace stops, some paint).

You're still supposed to drive around the circle though, right? Or am I misunderstanding?

That intersection you showed is clearly big enough. This one doesn't look big enough. Or is it? There are smaller intersections than this one, also. (And I realized that this one might be a bad example because it's not four directions.)

https://goo.gl/maps/fBEysywZgdQVWH7N9

The north and south exits to the roundabout are 10.5m across, including the traffic islands; the west exit is 5m across. The 4-way junction you've linked to, the exits are 9.5-11 meters across.

At some intersections in the UK, the roundabout is literally a small circle of paint. The car doesn't really go "around" it because it's so small. It mostly exists as a visual cue that the intersection follows roundabout rules.

Ok, I was working under the impression that one must drive around the circle. If that requirement isn't there and it just changes how we work out who goes when then I can see that expansion wouldn't be necessary.

Yeah... I don't think those will work in the US until roundabouts are a lot more common.

The issue I've seen with them in the US is many US drivers ignore pretty much everything about the painted circle which creates a really dangerous situation. They treat those intersections like 4 way stops (including driving over the circle) and that's a major problem.

Not to mention that in large areas of the northern US, any painted road markings are likely to be covered by snow and ice a good portion of the year.

Yes, they recently rebuilt a large roundabout here - it connects two busiest roads in town - it was nerve-wracking to enter on a motorcycle before. Now they rebuilt it with trafic lights and a straight lane underpass for the main road and it's much more pleasant.

Concur with your thinking.

At the same time, I took "abolish traffic lights" as a North Star for future design as well as making changes to existing infrastructure where economically and physically feasible (i.e. stay practical). Not rip out all traffic lights everywhere and replace them with roundabouts or rotaries, as the case might be.

My city has been going roundabout happy over the past few years. One issue they've had to contend with is existing intersections in congested urban areas don't have enough space to replace with a roundabout. Therefore it's been primarily the suburban areas that have been able to implement them.

And then you get roundabouts with traffic lights like in the UK. I'm sure there are good reasons for that, but, as someone that hardly drives in the UK, I was very very surprised the first time I encountered them.

Oh, that's nothing. Here in New Jersey, we have what my wife refers to as a "traffic theta". Here's an example:

https://www.google.com/maps/@40.7957351,-74.3405952,17z

It's a circle, with traffic light, but also still an intersection. Fun!

You generally get these when the roundabout has one or more clear 'through traffic' routes, to the point that you're always 'giving way to the right' and not able to enter the roundabout.

If you imagine traffic on a motorway going North/South and an A-road running East-West, at busy times, the traffic going from East to West and West to East will be significant enough that traffic coming off the motorway is not able to find enough space to enter the roundabout (or, not enough to meet the demand). Without traffic lights, traffic will soon back up down the slip road onto the motorway, or worse, will try to force its way onto the roundabout instead of giving way to the right.

Traffic lights make this much safer.

Or some arrangement of flyovers, ramps, etc (double diamond interchange being the current flavor of the month here in the US mid-Atlantic). Obviously, only makes sense for actual motorways, not going to get one in mid-town London, hopefully.

Land is expensive enough, and built up enough, in the UK that flyovers are pretty much not an option near any major road anymore.

In general the UK has very few flyovers. I sometimes suspect the SF Bay Area has more flyovers than the entire of the UK.

In addition, in areas with very high traffic, like London, area-coordinated adaptive traffic light systems (see SCOOT/SCATS) are used to keep traffic flowing smoothly, stop congestion from blocking junctions, prioritise emergency services and more. These systems are very good at what they do.

Traffic lights are also used to give priority to pedestrians and cyclists on junctions where it would be unsafe to rely on zebra crossings or pedestrian priority - think sharp and low visibility corners.

As far as roundabouts go, the UK has been replacing big multi-lane roundabouts in areas with lots of pedestrians and cyclists with two-way-traffic horse shoes (e.g. Old Street and E&C, plus others outside of London). This allows the centre of the roundabout to be used as public space, and has been found to be safer for vulnerable road users.

I'm all for light-free junctions where possible, and light-free roundabouts work REALLY well in low/medium traffic. But you can't just abolish traffic lights - unless we also abolish cars at the same time.

Do you have a link to one of these "two-way horse shoes" on Google maps or similar? I'm curious how they solve the problem of needing to taking the 3rd exit on a multi-lane roundabout while on a bicycle.

Pretty simple. The section of road between 3rd exit and the 4th (which is also where you enter) is completely removed.

So taking the 3rd exit on a bike either means following the road all the way around, or just going directly from the entrance to the 3rd exit, as cycle lane is usually preserved where the road used to be.

I looked at that E&C "horseshoe" - it still looks hairy if you're riding north on the A3 and want to turn right into the A201, given the number of crossings of busy roads with no traffic signals. But better than some of the busy 3-lane roundabouts I've had to navigate here with no provision for bicycles (or pedestrians really) at all.

Every junction on the E&C horseshoe if traffic light controlled, including all the cycle crossings.

The safest route for bikes is to take the segregated bike route at the bottom of the horseshoe, then using the mixed bike and pedestrian crossing to go directly over the mixed used paved area, then use the mixed crossing on the other side to join the A201. Either that, or use the segregated cycle path, then horseshoe near London Rd.

But honestly, on a bike you would just avoid the horseshoe completely. There’s usually better cycle routes that are more direct, and avoid large junctions like the E&C horseshoe.

Look up the Old Street roundabout and Elephant and Castle Roundabout.

The essence of of is segregated cycle lanes with cycle-only traffic lights. Nothing magic.

Neither of them are fully separated (yet at least - they're still being worked on), but they're a lot better than what came before.

Trafalgar Square also used to be a roundabout back in the day, though it got converted to a peninsula before bicycles were fashionable so that's not a great example.

Highbury Corner is another example you can look at.

Highbury looks to solve it by having traffic lights explicitly for pedestrians/ bicycles to cross at?

Didn't read the article but flyovers maybe expense but can get the job done. Wish there were more of them at major intesections

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