Stroad vs. Stroad: Land Use, Traffic Engineering, and What Happens When Suburban Arterials Intersect

dateline tuesday june 14th nevada primary election day the scene a typical suburban intersection in america's sun belt buckle up your seat belts everyone because today we're going to look at what happens when strodes collide this is city nerd weekly content on cities and transportation or maybe more accurately today suburbs and transportation and you know i just love making top 10 lists of terrible infrastructure when i did my video on pedestrian over crossings which featured the intersection of las vegas boulevard and tropicana avenue i kind of wondered aloud whether this was the largest signalized intersection in the u.s or even the world based on the absolutely absurd number of approach lanes 29 and all luckily this is the internet so it took like an hour tops for one of my trusty viewers to correct me nathaniel santiago pointed out that sr-7 and forest hill avenue in west palm beach actually has more approval ins well trust but verify right so let's check it out i actually count 31 approach lanes here and that's not even including the i don't know bike lanes that are squeezed in between the through lanes and the right turn lanes can you even imagine trying to bike through this intersection anyway this got me pretty excited about the possibility of doing like a 10 most offensively large intersections video but to be honest i wouldn't even know where to start with that i mean maybe they're all in florida so instead what i'm going to do today is take a deeper dive into a local example so that we can really understand the disaster that unfolds when two strokes intersect the contortions traffic engineers have to go through to make it all quote-unquote work and how people who have to navigate it without a car are usually complete afterthoughts so quick refresher on what a strode is it's an arterial that attempts to fulfill both the commercial purposes of a street and the speed and throughput purposes of a limited access roadway and in attempting to achieve both of those goals it manages to make a hash out of the whole thing so strodes are in and of themselves bad but what i want to focus on today is maybe the most offensive part of the whole thing which is what happens when two of them intersect i referenced this in my strodes video from a while back where i counted up the approach lanes on the northbound decatur leg of its intersection with charleston in west las vegas but today i want to look at a more suburban location that really reflects the design decisions that characterize suburban transportation planning and policy in the u.s and for that i'm going with the intersection of saint rose parkway and eastern avenue in henderson nevada let's take a quick tour of these two beauties so we can see what we're getting into in traffic engineering when you do an intersection study you look at a pretty wide influence area maybe a quarter mile in each direction looking at upstream and downstream signals cross streets driveway accesses land uses anything that might affect traffic flow through the intersection so let's take a tour around the influence area and look at some typical strude land uses big box stores set like a country mile back from the street with acres of surface parking check drive-throughs which are endemic destroyeds drive through banks for sure drive through coffee joints but it's really the drive-through fast food places i mean nothing says suburbia quite like sitting in your car for 20 minutes in line waiting for like some chicken tenders and fries you're gonna eat off your lap while you have one hand or maybe just a knee on the steering wheel the thing about this part of america and you may not properly understand this if you live in another part of the world i'm talking about drive-throughs that require their own coned off areas and specialized traffic logistics just to keep the cue from blocking adjacent travel lanes and drive aisles it gets really hairy at a place like in and out and heaven forbid you have a craving for a religiously sanctioned fried chicken sandwich because that requires a double lane drive through these places are built like i don't know new jersey toll plazas what else well wing joints including the best wings in town no not this place i mean this one money laundering operations i mean mattress stores gun shops glorified ham and egg shops shops that sell both beef and pizza purveyors of fine beverages i compared the strode to an ecosystem in my earlier video well it's not just a metaphor even in a desert that's almost completely paved over the habitat teems with wildlife the larger point here is all these land uses in the intersections influence area are big trip generators so it's not going to be uncommon for someone to travel through this intersection multiple times on the same trip which really just exacerbates all the problems so let's take a look at intersection geometry these are strodes we know they're big streets and if you look upstream in each direction to check the typical cross section eastern is three through lanes and saint rose is four through lanes these are really big footprints as it is but look how they widen out as you approach the intersection this kind of has a sick logic to it if you think about it because a signal basically cuts throughput in half or worse so you kind of need something like double the approach lanes through the intersection to provide the same capacity as whatever the typical cross-section is upstream and downstream it's really perverse after all the intersection is where you actually need the most space for things like signal poles and cabinets ada ramps pedestrian cueing so there are a lot of competing needs you have to balance yet over and over again the priority is to provide as many turn lanes as possible to increase the capacity of the intersection in traffic engineering there's actually a term for this which is blowing out the intersection the other thing you do as a traffic engineer to get the most capacity out of the intersection is optimize the signal timing usually this means very long cycle lengths and in the middle of the day at this location we're talking 180 seconds three minutes long the explanation for this is when you have a very large intersection there's a significant amount of what we call lost time that's built into each phase to explain this let's talk about the signal cycle at this particular intersection this is a six phase cycle first phase is an eastbound through with a leading protected left turn followed by an eastbound westbound through then it combined westbound through and lagging protected left then we go to a southbound through and leading left i combined northbound southbound through and finally a northbound through and lagging left the cycle length varies a bit but it runs with 180 seconds at busy times these are typical phase lengths i observed but they're going to vary depending on how much demand is detected for each movement and whether there's a pedestrian call for one of the crosswalks which i'll talk more about later in the video so let's get back to lost time the actual equation for last time is more complicated and includes things like how late drivers will still enter the intersection on a yellow even though they shouldn't and driver's reaction time to start up after a signal turns green but a simple way to think about it is it's the sum of the yellow time plus the all red time if you don't know what all red is there's a short period after each phase where you keep everything red to ensure all the movements are completed generally the bigger the intersection is the more yellow time and all red time you need to clear the intersection and prevent t-bone collisions so for each phase at this intersection i observed something like 4.5 seconds of yellow time and 2.5 seconds of all red these will be smaller numbers at smaller intersections but for monsters like this that's something like seven seconds you lose out of the cycle for each phase so what this means is to reduce the proportional impact lost time has on the entire cycle length you want to make the cycle as long as possible within reason and a really big limiting factor is the longer the cycle length is the more q storage you need in your turn lanes and look at how long these bad boys are and worst of all is how this impacts people walking biking and rolling through the intersection which i'm going to get to in just a bit but first the usual reminder to drop a like on the video if you enjoy detailed explorations of intersection ops and really who doesn't subscribe and hit the bell if you want content like this every week consider joining the patreon link in the description if you want to ensure that i don't have to advertise like weird crypto stuff on this channel just to stay financially solvent and let's check the sub count i did hit 50k subscribers this past week so thanks to everybody who's been joining up i had a lot of stadia i could have gone with this week but i really can't pass on yankee stadium it isn't the original but it's still iconic in its way and even if there's just way too much parking the train access is absolutely top notch i'm not really a yankee fan at all but i am a yankee stadium fan so let's talk about how this monster intersection accommodates or doesn't accommodate people who aren't driving first of all a couple key pieces of information i left out when i was setting the scene transit line 110 runs on eastern and is one of rtc's busiest routes and as always with transit riders have to cross the street at least once either on their way to board the bus or after a lighting from it also saint rose does not have sidewalks instead it has a multi-use path which is complete on the south side and actually pretty good for biking and there's a less useful one on the north side the result is you get a lot of people biking across the south leg of the intersection in addition to all the other people who need to cross so what i haven't talked about yet is these slip lanes with the pedestrian islands which honestly in the biz we use the highly technical term porkchop really it's as if the traffic engineers have done everything they can think of to make crossing this intersection as unpleasant as possible first you have to cross the slip lane which you would think would be straightforward like there shouldn't be confusion about who has the right of way here after all there's a crosswalk and a yield sign but if you've crossed a suburban intersection like this at any point in your life you know in practice about 75 percent of cars just completely disregard whether there's a pedestrian trying to cross then when you get to the island it's noisy there's debris all over the place that makes you wonder how safe you really are walking there and here's something really fun huge skid marks on the island itself good times so everything about this is designed for the convenience of people driving cars so they're minimally impeded when they're trying to turn right the islands are uncomfortably small so if you're in a group riding bikes you have to crowd onto the island like how does this work if you have kids with you also if you show up at the wrong time like in the middle of the eastbound phase they're not going to extend to the green to give you a walk signal so get ready to wait about three minutes three minutes is a lot of time to be waiting in a place like this as for the pedestrian push button itself how the timing for walk and don't walk indicators is calculated and how well people understand them well i covered that in my video on pitt over crossings but this tweet basically sums up my feelings on the subject the last characteristic i want to mention before we leave here is the posted speeds on the streets eastern is posted at 45 miles per hour which is depressingly typical for this kind of suburban arterial saint rose though is a state highway not that that excuses it but it's signed at 55 miles per hour oh yeah and apparently the striped shoulder is totally appropriate for people walking and biking traffic goes 60 plus here it's not a limited access highway it's a suburban arterial that has signalized intersections and driveway accesses on it it's just complete madness and i'm not going to show it but there's a roadside memorial at the southeast corner of the intersection where vigils are still held from time to time you see a couple months ago a driver who was stopped at the signal on the westbound approach of saint rose was struck from behind by another car the first driver's fuel tank exploded and well there's a roadside memorial so there's nothing about the design of these streets or the intersection where they converge that really convinces me human health and safety are a high priority how a signalized intersection is designed and operates is really a statement of a city's values or maybe even the values of wider u.s suburban culture if you have inhumanly large intersections with high speeds and three-minute cycle lengths it's a very clear indication that your city values personal motorized vehicle throughput above really everything else okay that's all the super uplifting content i have today thanks for watching and thanks as always to the patrons who keep this channel running like the well-oiled machine it is i will of course be back with a new topic next week and i'll see you then

Channel: CityNerd

Views: 197,063

Keywords: urbanism, urbanist, urban, henderson, henderson nevada, urban planning, strong towns, charles marohn

Id: 3v537SEfDag

Length: 14min 44sec (884 seconds)

Published: Wed Jun 22 2022