[HN Gopher] Mapping pedestrian traffic light timing in Sydney, A...
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Mapping pedestrian traffic light timing in Sydney, Australia
Author : jakecopp
Score : 67 points
Date : 2023-06-12 22:37 UTC (1 days ago)
(HTM) web link (jakecoppinger.com)
(TXT) w3m dump (jakecoppinger.com)
| streamfrog wrote:
| When I moved from Europe to Sydney, it was striking how much
| traffic lights deprioritised walking. Visitors have independently
| commented on similar things.
|
| Its not just timing, but also inefficient phases. I requested the
| dataset for phases, but after months was given a totally
| different dataset. I gave up.
| gtmb wrote:
| Australia is at least 40 years behind in traffic management.
|
| There is no traffic lights priority for public transport.
| Melbourne's tram avg speed is 10-15 kph. If you power walk you
| can go faster than the tram. It just sits there waiting on
| traffic lights more than moving.
|
| There is no synced traffic lights. On long avenues you just
| stop every 200m because once the light goes green when you
| arrive at the next intersection the light there goes red. It
| seems it is synced, but to the opposite it should be doing.
| madeofpalk wrote:
| Sydney's traffic light system (Sydney Coordinated Adaptive
| Traffic System, or SCATS) is supposedly "a recognised
| worldwide market leader in intelligent transport systems" and
| has been exported to a bunch of cities around the world. It
| does (supposedly) prioritise public transport in phase
| timings.
|
| https://en.wikipedia.org/wiki/Sydney_Coordinated_Adaptive_Tr.
| ..
|
| > On long avenues you just stop every 200m because once the
| light goes green when you arrive at the next intersection the
| light there goes red. It seems it is synced, but to the
| opposite it should be doing.
|
| I recall a link a while back (from HN?) that demonstrated
| that it's basically impossible to sync green traffic lights
| in both directions. Any attempt at syncing will priotitise
| one direction over the other. I can't find the source, and it
| was so long ago that it's very likely that I'm
| misremembering.
| contingencies wrote:
| Re. SCATS, I used to work at the RTA as a consultant for
| another company back in ~2000 when it was still based as
| Eveleigh. My understanding is and has always been that they
| were the ~first to put loops under the road to count
| traffic but the other elements of the system were not that
| amazing. They still had a PDP live, and also ran the Sydney
| portion of the emergency services radio network from the
| same data center. A control system would show real time
| traffic densities. We were adding a PTZ-capable remote
| video on demand component circa 2000 using a combination of
| 128K ISDN and fiber. I wrote some kind of last minute
| multiplexing PTZ data control bridge kludge in perl. The
| idea was that, after the traffic system detected an
| anomaly, the control system operators could "dial in" and
| "look around" to "determine" the cause of traffic issues
| and create an appropriate response using their bridgedeck
| mounted joysticks straight out of the 80s. We sold some to
| the Philippines and I got to go, as an 18 year old, and
| party hard with the locals after we signed a deal with the
| mayor of Manila. Fun times. Corrupt as knifespoon.
|
| These days I assume most people/companies/governments
| source their traffic flow info from Google because it has
| more 'active' sensors in so far as every car has at least
| one mobile phone. Telcos could and should also sell this
| type of data in an anonymous format. Large toll roads track
| individual vehicles with a combination of wireless billing
| systems and numberplate ID so they are effectively able to
| provide a similar solution for those high value roads.
| iggldiggl wrote:
| > it's basically impossible to sync green traffic lights in
| both directions.
|
| For a bi-directional green wave, intersections have to be
| spaced at intervals consistent half the cycle time (times
| the intended travel speed) of the traffic lights. In that
| case opposing vehicle streams will always meet each other
| at an intersection, thereby minimising the green time
| required along the green wave and maximising the green time
| available for handling crossing and turning traffic.
|
| If an intersection deviates from that mathematically
| optimal location, it means that there'll be less of an
| overlap between the green times for the two opposing
| direction, meaning that there's less green time left over
| for cross traffic.
|
| And since in real life, intersections are rarely spaced at
| the mathematically optimal interval, in practice this means
| that eventually you have to give up and just favour one
| direction depending on the time of the day. (To some extent
| you can try to salvage things by varying the assumed speed
| between intersections in order to keep the travel time from
| intersection to intersection constant, but there's only a
| limited usable speed range between too slow and the legal
| speed limit.)
|
| And if you attempt to have multiple green waves crossing
| each other, you introduce even more scheduling constraints
| which might leave no room for a perfect solution.
| csunbird wrote:
| Germany does it very well. Until I make a turn, I do not
| wait at red lights more than once or twice.
| shortcake27 wrote:
| Melbourne is the same. Buttons that change the timing are rare
| or maybe even non-existent. I can't think of any intersections
| where pressing the button does anything other than activate the
| pedestrian lights.
| Someone wrote:
| > Buttons that change the timing are rare or maybe even non-
| existent
|
| Buttons are old tech.
| https://www.flir.com/products/trafione/:
|
| _"The FLIR TrafiOne uses thermal imaging and Wi-Fi
| technology to adapt traffic signals based on the presence
| detection of vehicles, bicycles and pedestrians, even in
| total darkness or adverse weather."_
|
| I don't know how smart that version is, but there are
| versions that predict whether pedestrians have the intention
| to cross the street. https://www.tugraz.at/en/tu-
| graz/services/news-stories/tu-gr...:
|
| _"The innovative camera-based system recognises the
| intention of pedestrians to cross the road and switches to
| green automatically. What's more, it optimises the traffic
| flow further, as Horst Possegger from the Institute of
| Computer Graphics and Vision explains by way of two examples:
| "The green phase can be extended in the case of large groups
| of persons, who require more time to cross the road. And if
| persons leave the waiting area before the lights have turned
| to green, this is also passed on to the lights. The traffic
| lights subsequently don't switch to green and there are no
| unnecessary waiting times for motorised traffic."
|
| [...]
|
| "Using the current configurations, our system signals that
| wish to cross three to four seconds before the button is
| pushed," says Possegger."_
| reaperman wrote:
| Feels like you could do that somewhat cheaper with just
| visual cameras and any off-the-shelf YOLOv# detection
| model.
| kimixa wrote:
| For the pedestrian problem at least, it seems even
| cheaper to just use a button. That also completely
| bypasses the problem of trying to detect if they intend
| to cross. Is there really much of a disadvantage? The
| pedestrian has to be in a specified area beside the
| crossing already to use it, so likely within arms reach
| of a pole already. But I can see it being useful for cars
| and bikes - as a cyclist I've hit a good number of times
| the magnetic sensors clearly just don't work for a bike,
| and had to wheel over to the pedestrian crossing to press
| the button to get the lights to change.
|
| And I expect "person detection" to be much easier with an
| IR image, there's probably not many places where human
| body temperature isn't noticeably higher than the
| background should make it more accurate to pick out. And
| if you don't need accuracy of temperature reading, an IR
| camera isn't really any more expensive than a visual
| camera - it's the same CCD just with a different filter
| on top. And it completely bypasses any problems of
| darkness.
|
| I also wouldn't be surprised if the actual camera unit
| was a near negligible cost of installing something like
| this, so even if it was multiples of the price,
| optimizing for that may be the wrong target if it affects
| accuracy at all.
| [deleted]
| iggldiggl wrote:
| > Is there really much of a disadvantage?
|
| Granted it's probably nothing too big in absolute terms,
| but does feel a little unfair, because vehicles usually
| get a few seconds head start for free due to being able
| to call a signal as soon as they reach the location of
| the green extension detector, which can be a few tens of
| metres in advance of the stop line.
|
| (On the other hand yes, I do acknowledge the because
| "turning lanes" don't really work for pedestrian traffic,
| it's often hard to detect pedestrians much in advance
| because you'll have no idea which way they'll want to
| turn at the intersection. But it still feels a little
| unfair :-) )
|
| And unless the default state of an intersection is "red
| for all directions", switching the lights will always
| take a few seconds even in the best of cases. By giving
| the traffic lights controller some advance warning of
| somebody approaching, it's possible to switch the traffic
| lights just in time so that that user doesn't have to
| stop (if traffic conditions allow it of course - with
| heavy traffic it's unavoidable that _somebody_ will have
| to wait eventually).
|
| With semi-flexible traffic light designs (where phase
| length and whether a phase is called at all depends on
| traffic conditions, but otherwise they still always cycle
| through the phases in a fixed sequence), there are also
| situations where a signal can only turn green (if called)
| until a certain point in the cycle no later than X (in
| which case it'll remain green until let's say for example
| X + 10 seconds). If you miss that time X, you'll have to
| wait a whole signal cycle until the signal can turn green
| again. If it just happens that you're reaching the
| intersection at a time X + 5 seconds, it means that if
| you could have called the signal while still six seconds
| away (i.e. at X - 1 second), you still could have crossed
| successfully (because in that case the signal would have
| been green between X and X + 10), whereas without that
| possibility you can only press the button at X + 5
| seconds and now have to wait one whole signal cycle.
| bobthepanda wrote:
| I have never seen an intersection where beg buttons favor
| pedestrians and not drivers, because beg buttons give
| engineers the latitude to establish red crosswalks unless
| requested. So help you if you arrive just in time to miss
| your activation cycle and have to wait a full light cycle for
| the crosswalk.
| danhor wrote:
| I've seen quite a few intersections (Germany) that only
| feature one car road, but a crossing pedestrian/bike street
| that after pressing the beg button immediately begin to
| switch the light, resulting in a consistent, short wait
| (apart from signal priority stuff for busses). But anything
| more complicated, nothing comes to mind.
| Someone wrote:
| https://bicycledutch.wordpress.com/2016/06/21/traffic-
| lights... has plenty examples of things more complicated,
| for example:
|
| _"In the past, buses always got priority. Now every bus
| is tagged and the computer knows all the time-tables of
| every line. The system knows exactly when which bus needs
| to arrive at a certain intersection. The installation
| checks whether a bus is too early, on time, or running
| late and sets the lights accordingly."_
|
| _"On the cycleways we always have double loops,
| separated by 75 centimetres. That way we can measure
| speed and direction by combining the data the computer
| receives from the two loops. It also means we don't need
| to reserve green time for a cyclist riding against
| traffic, away from the intersection." And the pushbutton?
| "For cyclists that's not really necessary. They're only
| there for reassurance. You often see in the reports that
| people don't even bother to push the button."_
| bobthepanda wrote:
| But there the priority is pretty much everything else
| other than the beg button.
|
| I can't help but wonder if such aggressive timings
| discussed in the article are good for people with
| disabilities. People often panic when rushed by a change
| to red.
| toast0 wrote:
| I've experienced plenty of beg buttons that don't do
| anything other than activate the crossing light when that
| direction next goes green for cars. But also plenty where
| pressing the button takes immediate steps for the
| pedestrian: if the direction is already green for cars, the
| walk sign is turned on; otherwise, the current cycle ends
| and any intermediate cycles proceed with minimum duration;
| non-dominant directions will have longer minimum cycle time
| if the pedestrian button has been pressed.
|
| In my experience, if the intersection processes car traffic
| dynamically, it will also process pedestrian traffic
| dynamically, and generally favor pedestrians. If the
| intersection has static timing, it's not going to do
| anything different for pedestrians. I recall driving in
| Milwaukee near UWM two decades ago, every morning I could
| count on the lights showing exactly the same thing at the
| same time. If I left my apartment at the same time, I'd get
| the same sequence of missed or made lights. Most other
| places I've driven had car sensors (usually loops in the
| pavement, but cameras are cheaper and less maintenance
| now), so there's no schedule to be learned, although the
| behavior is predictable if you learn the cycles and observe
| the stimuli. (Although, sometimes sensors are broken or
| miswired; there was an intersection near one of my
| employers where the cyclist button was connected as an left
| turn lane occupancy sensor; resulting in consistently wrong
| behavior. it's also not uncommon for a disabled vehicle to
| be located above a loop, or sometimes a construction /
| utility vehicle to be parked above a loop; some control
| systems can adapt and filter that out, but many don't.)
| rconti wrote:
| Don't forget the infuriating situation where infra
| designers/whomever decide "we can't put a sidewalk here", or
| governments allow construction to close a sidewalk for years on
| end.
|
| Why it's acceptable to put up signs saying "don't cross here" and
| instead require that people cross the road 3 times to go a few
| dozens of feet is beyond me.
| fatnoah wrote:
| > Don't forget the infuriating situation where infra
| designers/whomever decide "we can't put a sidewalk here", or
| governments allow construction to close a sidewalk for years on
| end.
|
| My favorite instance of this happened when the town decided to
| improve the dodgy sidewalk that followed a busy road. The
| sidewalk was in rough shape, and while it was walkable, it
| would have been impossible for anyone with a mobility
| impairment.
|
| Improving the sidewalk meant that it was closed for almost 8
| months. During that time, I had to walk at the edge of the
| vehicle travel lane. As winter approached, they finally
| finished construction and I enjoyed the beautiful condition of
| the new sidewalk...for about two months. After the first snow
| storm, it became impassible and, for reasons I never found out,
| the town never plowed it again. So, I had the option to travel
| back in traffic, or trudge through the snow. The situation
| ended up being a factor in me giving up and buying a car.
| leothelion_ wrote:
| I'd very much like to see for Melbourne!
| secretsatan wrote:
| I've been meaning to time the traffic lights where I am, most are
| really good for pedestrians, but there are some here and there
| that take an age to change. I even changed my walk to work as the
| shortest path has a couple of particularly slow crossings, making
| a slightly longer route quicker as it only has zebra crossings.
| kfarr wrote:
| This is awesome, and I'd add that in doing safe streets advocacy
| in SF I have learned that to make changes like these it's helpful
| to record the entire signal timing for all phases to make more
| concrete recommendations for changing timing. In other words
| you'll have to take time from other signal phases to increase ped
| timing and without that data it's hard to advocate for change.
| Here is one example of a full phase visualization:
| https://glitch.com/edit/#!/aframe-ped-signals?path=README.md...
| ninesnines wrote:
| This is actually one of the most annoying things I've noticed in
| Brisbane - the lights for walking take absolutely forever. To the
| point that everyone will j walk because it can take 5 minutes for
| a light to change; it makes getting around the city so
| frustrating as a person coming from Northern Europe
| blindstitch wrote:
| In the USA, the Manual of Uniform Traffic Control Devices has an
| (I think) reasonable requirements for crossing durations but
| almost no further recommendations about maximum wait times. This
| results in completely idiotic timing programs of the signals
| everywhere that encourage people to cross when cars have a green
| light. If you want to change it to be more pedestrian friendly,
| it can cost $20k+ because the signals are programmed in a 40 year
| old language that only a very small group of highly paid traffic
| engineers know how to write.
| lostlogin wrote:
| > If you want to change it to be more pedestrian friendly, it
| can cost $20k+
|
| Per set of lights?!
| unflxw wrote:
| > the signals are programmed in a 40 year old language that
| only a very small group of highly paid traffic engineers know
| how to write.
|
| This is interesting. What language is this, or more generally,
| where can I read more about this?
| nwahs_op wrote:
| If you are super bored. Here is a manual that is VERY
| detailed explanation on programming traffic signals. I give
| this to new engineers and technicians to look at when they
| first start.
|
| Chapters 5 and 6 get into the actual programming of the
| signal.
|
| https://ops.fhwa.dot.gov/publications/fhwahop08024/index.htm
| yamazakiwi wrote:
| Traffic light systems are designed using software such as
| LINSIG, TRANSYT, CORSIM/TRANSYT-7F or VISSIM.
|
| Per wikipedia different countries use different systems over
| time:
|
| e.g. Sydney: 3,400 traffic signals co-ordinated by the Sydney
| Co-ordinated Adaptive Traffic System (SCATS). Designed and
| developed by RTA, the system was first introduced in 1963 and
| progressively developed since then. By October 2010, SCATS
| was licensed to 33,200 intersections in 144 cities across 24
| countries worldwide, including Singapore, Hong Kong, Dublin,
| Tehran and Minneapolis and Detroit.[19][23][24]
|
| https://en.wikipedia.org/wiki/Traffic_light_control_and_coor.
| ..
| mschild wrote:
| edit: Whops. Just realized theyre talking about the US.
| Disregard my comment.
|
| I'm not entirely sure what OP is talking about, but I think
| they use a system called SCATS.[0] Looks like the system is
| actually pretty widely used in some other countries as well.
|
| [0] https://www.scats.nsw.gov.au/solutions/products
| nwahs_op wrote:
| I happen to be a traffic engineer who operates signals in the
| USA. We may not have the most advanced technology but I can
| assure that we don't not write code to operate our signals. We
| do enter different parameters that govern the amount of time
| that you have to wait.
|
| In most situations it comes down to if you want to favor
| vehicles or if you want to favor pedestrians. As everyone has
| mentioned it is difficult to accommodate both as they would
| like.
|
| Also as government worker I can assure we are not highly paid.
| We make a decent living but there is actually a shortage of
| people right now that want to do the work.
| jakecopp wrote:
| Transport for NSW, the government agency which controls traffic
| signal timing in Sydney and NSW, has an excellent stated goal of
| increasing walking and cycling trips - and reducing pedestrian
| wait times at intersections.
|
| However, there is no public data on traffic light timing in
| Sydney or NSW.
|
| I built this little React site to crowdsource measurements and
| inform where positive changes could be made - Sydney focused, but
| works anywhere in the world if you'd like to make use of it/fork
| it!
| joppy wrote:
| Thanks for making this! I've found that as a pedestrian in
| Sydney, up to half my walking time is spent waiting for traffic
| lights, and have always wondered what could be done about it.
| rozenmd wrote:
| I wonder if the $75 fine for jaywalking and NSW Police's love
| for issuing these fines are related to how long the timings
| are.
| robbiep wrote:
| Just cross back from the crossing. It's legal (?not illegal)
| to jaywalk in NSW if you are more than 20m from the nearest
| designated crossing, if you are not interfering with traffic
| (section 234). I've never met anyone who has received a fine
| for crossing at the wrong time?
| rozenmd wrote:
| Most folks in the city just walk through the red light when
| there's no traffic - I've seen them fine folks in waves
| around Central and Town Hall.
| riekus wrote:
| As an European which spend 4 years in Sydney recently I
| was always surprised at the opposite. Every after going
| out at midnight, Hurds of people would be waiting for a
| red light with no car/traffic in sight for a mile. I
| always jaywalk, feel particularly upset that a computer
| is telling me to wait for a save time, without context,
| while I can obviously tell it's save.
|
| Recently discussed this behaviour in Sydney, remember it
| was particularly bad around Surry hills
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