You are correct.... It happened in a city in Finland.
https://www.reddit.com/r/CitiesSkyl...y_in_finland_is_holding_a_design_competition/
I already know that I’ll work If the objective is purely aesthetic. My doubt is related to the traffic and the city behavior after changing It.
Hi Almir,
I’ve been thinking about the fused grid district design (fusedgrid.ca) and how it can be improved for both game/simulation and real life. Living in the Seattle area and having lived in other large cities with snarled traffic and varying road/street strategies, and also being a software engineer by trade (so I know how the traffic routing algorithms work, for example) and I’ve decided on a number of design rules to follow for street/road layout to maximize flow and minimize gridlock/deadlock problems:
1. Only local neighborhood roads are bidirectional.
2. Roads in the larger grid are one-way streets, 2 lanes wide.
3. Where you have parking along the roads/streets, it’s angled back-in parking.
4. Where a two-way street/road meets with a one-way street/road, for right-hand side driving, the two-way roads are always a right-turn off of the one-way street going in the direction of the one-way street.
5. Never cross a one-way street with a two-way street.
6. Use roundabouts instead of traffic lights.
7. Use grids in dimensions of fused grid generally to make it very walkable and optimized for mass transit.
8. Provide dedicated areas for bus stops.
9. Favor use of one-way couplets (two one-way streets a block apart) instead of wide bidirectional streets.
Now, an explanation is in order for these design rules: they’re all designed with most efficient flow in mind for the overall amount of travel and pavement, while also being very walkable.
1. Since these will be residential streets where only people living there will go in and out (a major part of the fused grid concept) there won’t be enough traffic to require many lanes in any direction, and foot traffic will be able to deal with vehicular traffic easily enough. Allowing bidrectional streets there allows for enough redundancy in case vehicles or other things block off flow. With a single lane of travel in each direction, that should be sufficient, especially with angled back-in parking. By having angled back-in parking on both sides of the street, you can completely eliminate driveway aprons to cross on foot, as long as the neighborhood is of a modest to low density: once it is a high enough density to require more parking than works that way, build parking garages that open onto the street where back-in parking was, and make it underground perhaps only for the entrance, but above ground for the rest, as underground parking garages get absurdly expensive to build. This way preserves the pedestrian walkability on the sidewalks, as there will be no conflicts with cars pulling in or out of parking.
2. Why 2 lanes wide? I’m a software engineer by trade, and there’s something called Amdahl’s law, which deals with scala ility between more than one CPU core: in many tasks, too many things need coordination, and adding more cores doesn’t always lead to having it run faster due to all that coordination, and definitely not a linear scaling where doublng the number of cores doubles efficiency. Once you add enough cores, it actually can end up takng more time than only having a single core, in the worst-case scenario. People switching lanes for turns or just to go faster results in lower scaling efficiency, so 4 lanes in heavy traffic can actually slow down more than 2 lanes, if people are jockeying for position too much and making other lanes wait while they block them. It only takes 1 car straddled between 2 lanes to keep those 2 lanes from being useful. The reason drivers are most likely going to do that is to get to a turn before they run out of road: if you have multiple lanes to cross in a short distance and traffic is heavy, you can’t just quickly move from the farthest to the nearest lane you need to be in for your turn, and the result is slowing down traffic overall. If you only have 2 lanes going in the same direction, while someone is currently turning, you can usually pass them in the other lane; if you need to turn off and you’re currently in the other lane, you only need to change one lane. Note: this needs to be tested in the real world to see how typical drivers behave
Also, if a road is only two lanes wide, it can be crossed much more easily on foot in a shorter time, meaning shorter traffic cycles are needed where people are stopped. Of course, this is also eliminated when there are roundabouts, but widths still matter.
3. Angled back-in parking is safer for all involved compared to parallel parking for getting in and out of cars, and adds a steel barrier between traffic and the sidewalk, and also helps tame traffic speed. It’s also easier and faster for most to back in rather than parallel park, and additionally, you aren’t as likely to end up with a bunch of spaces too small to park in.
4. By keeping two-way streets such that they’re on the right-hand side when drivng on the right-hand side, this means turning onto the two-way street from the one-way street is a right turn, and so is turning onto the one-way street from the two-way street is also a right turn that never results in travel across opposing directions, so there’s no conflicts in that regard. There is never a need for a left turn and the turning cycle cost as a result, and nobody trying to get into the lane gets trapped blocking a lane of traffic. If you do use traffic lights, you can always do a right turn on red!
5. Like #4, this keeps you from ever needng to worry about traffic getting blocked or from ever needing a left/center turn lane, especially since only local streets with light traffic are two-way.
6. Traffic lights require traffic to stop, often for long periods of time, when opposing lanes in the intersection have nothing blocking in the way. This itself can lead to gridlock as a result of one direction of traffic backing up and affecting what the perpendicular traffic can do. Some systems that sense traffic can adapt for this by changing light cycles, but that also means people won’t be able to predict and maintain a consistent travel speed for very long. While you usually need to slow down for a roundabout, most of the time you never need to actually stop: you’re likely to average a higher overall speed than dealing with faster upper speed limit roads with long traffic light cycles.
7. You can easily get a viable transit system working if the routes go to useful places, which also requires walking not be too long on both ends.
8. Dedicated areas for bus stops reduces the disruption of buses loading/unloading passengers, imcreasing flow of traffic in general: much more efficient thsn addng whole lanes for more cars.
9. Couplets help reduce left/center turn lane contention by removing it by elminating the need for it, cmceptually: the connecting streets (also most likely one-way) provides a lot of room for people to queue up without contention, and just merging going into the opposite direction of travel, without stopping it needlessly.
