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<ol class="chapter"><li class="chapter-item expanded "><a href="../../index.html"><strong aria-hidden="true">1.</strong> Overview</a></li><li class="chapter-item expanded "><a href="../../howto/index.html"><strong aria-hidden="true">2.</strong> Instructions</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../../howto/map_parking.html"><strong aria-hidden="true">2.1.</strong> How to map on-street parking</a></li><li class="chapter-item expanded "><a href="../../howto/new_city.html"><strong aria-hidden="true">2.2.</strong> Importing a new city</a></li></ol></li><li class="chapter-item expanded "><a href="../../how_it_works.html"><strong aria-hidden="true">3.</strong> How it works</a></li><li class="chapter-item expanded "><a href="../../case_studies/index.html"><strong aria-hidden="true">4.</strong> Case studies</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../../case_studies/lake_wash.html"><strong aria-hidden="true">4.1.</strong> Lake Washington Blvd Stay Healthy Street</a></li><li class="chapter-item expanded "><a href="../../case_studies/west_seattle.html"><strong aria-hidden="true">4.2.</strong> West Seattle mitigations</a></li><li class="spacer"></li></ol></li><li class="chapter-item expanded "><a href="../../dev/index.html"><strong aria-hidden="true">5.</strong> Developer guide</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../../dev/misc_tricks.html"><strong aria-hidden="true">5.1.</strong> Misc developer tricks</a></li><li class="chapter-item expanded "><a href="../../dev/api.html"><strong aria-hidden="true">5.2.</strong> API</a></li><li class="chapter-item expanded "><a href="../../dev/testing.html"><strong aria-hidden="true">5.3.</strong> Testing</a></li></ol></li><li class="chapter-item expanded "><a href="../../map/index.html"><strong aria-hidden="true">6.</strong> Map model</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../../map/importing/index.html"><strong aria-hidden="true">6.1.</strong> Importing</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../../map/importing/convert_osm.html"><strong aria-hidden="true">6.1.1.</strong> convert_osm</a></li><li class="chapter-item expanded "><a href="../../map/importing/geometry.html"><strong aria-hidden="true">6.1.2.</strong> Road/intersection geometry</a></li><li class="chapter-item expanded "><a href="../../map/importing/rest.html" class="active"><strong aria-hidden="true">6.1.3.</strong> The rest</a></li></ol></li><li class="chapter-item expanded "><a href="../../map/edits.html"><strong aria-hidden="true">6.2.</strong> Live edits</a></li><li class="chapter-item expanded "><a href="../../map/misc.html"><strong aria-hidden="true">6.3.</strong> Misc</a></li><li class="chapter-item expanded "><a href="../../map/platform.html"><strong aria-hidden="true">6.4.</strong> Exporting</a></li></ol></li><li class="chapter-item expanded "><a href="../../trafficsim/index.html"><strong aria-hidden="true">7.</strong> Traffic simulation</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../../trafficsim/discrete_event.html"><strong aria-hidden="true">7.1.</strong> Discrete event simulation</a></li><li class="chapter-item expanded "><a href="../../trafficsim/travel_demand.html"><strong aria-hidden="true">7.2.</strong> Travel demand</a></li><li class="chapter-item expanded "><a href="../../trafficsim/gridlock.html"><strong aria-hidden="true">7.3.</strong> Gridlock</a></li><li class="chapter-item expanded "><a href="../../trafficsim/trips.html"><strong aria-hidden="true">7.4.</strong> Multi-modal trips</a></li><li class="chapter-item expanded "><a href="../../trafficsim/live_edits.html"><strong aria-hidden="true">7.5.</strong> Live edits</a></li><li class="chapter-item expanded "><a href="../../trafficsim/parking.html"><strong aria-hidden="true">7.6.</strong> Parking</a></li><li class="spacer"></li></ol></li><li class="chapter-item expanded "><a href="../../project/index.html"><strong aria-hidden="true">8.</strong> Project</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../../project/roadmap.html"><strong aria-hidden="true">8.1.</strong> Roadmap</a></li><li class="chapter-item expanded "><a href="../../project/motivations.html"><strong aria-hidden="true">8.2.</strong> Motivations</a></li><li class="chapter-item expanded "><a href="../../project/history/index.html"><strong aria-hidden="true">8.3.</strong> History</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../../project/history/backstory.html"><strong aria-hidden="true">8.3.1.</strong> Backstory</a></li><li class="chapter-item expanded "><a href="../../project/history/year1.html"><strong aria-hidden="true">8.3.2.</strong> Year 1</a></li><li class="chapter-item expanded "><a href="../../project/history/year2.html"><strong aria-hidden="true">8.3.3.</strong> Year 2</a></li><li class="chapter-item expanded "><a href="../../project/history/year3.html"><strong aria-hidden="true">8.3.4.</strong> Year 3</a></li></ol></li><li class="chapter-item expanded "><a href="../../project/CHANGELOG.html"><strong aria-hidden="true">8.4.</strong> Full CHANGELOG</a></li><li class="chapter-item expanded "><a href="../../project/references.html"><strong aria-hidden="true">8.5.</strong> References</a></li><li class="chapter-item expanded "><a href="../../project/collaborations.html"><strong aria-hidden="true">8.6.</strong> Collaborations</a></li></ol></li></ol>
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<h1 class="menu-title">A/B Street</h1>
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<main>
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<h1><a class="header" href="#initialmap-to-map" id="initialmap-to-map">InitialMap to Map</a></h1>
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<p>Still in the <code>map_model</code> crate.</p>
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<ul>
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<li><code>map.rs</code>'s <code>make_half_map</code>: Expand roads to lanes, using the list of lane
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types from before</li>
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<li><code>make/turns.rs</code>: Generate turns for every intersection.
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<ul>
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<li>Vehicle turns (for cars, bikes, buses)
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<ul>
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<li>Consider every pair of roads in the intersection. Try to match up lane
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types -- if there's a bike lane on both roads, don't add a turn from
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driving->bike or bike->driving. If there's not, then fallback to
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transitions between different lane types.</li>
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<li>Classify the turn based on the difference between the angle of the
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incoming lane's last line and the outgoing lane's first line
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<ul>
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<li>For straight turns, use the Cartesian product to link every incoming
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with every outgoing lane. If the indices dont match up, the turn becomes
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a <code>LaneChangeLeft</code> or <code>LaneChangeRight</code> turn. This is used later for
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intersection policies to prioritize turns appropriately.</li>
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<li>Right and left turns only originate from the one lane on the appropriate
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side</li>
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</ul>
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</li>
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</ul>
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</li>
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<li>Walking turns for pedestrians
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<ul>
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<li>Consider pairs of adjacent roads around the intersection
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<ul>
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<li>Make a crosswalk to the other side of the road, assuming there's a
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sidewalk on both sides</li>
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<li>Make a shared sidewalk corner over to the adjacent road</li>
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<li>If the adjacent road doesn't have a sidewalk on the close side, then
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consider skipping that road and making a crosswalk over to the next
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road. An example of this is a crosswalk over a highway on/off ramp.</li>
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</ul>
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</li>
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</ul>
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</li>
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<li>Verify all the turns so far are unique</li>
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<li>Filter by the OSM turn restrictions ("only straight" between road1 and
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road2)</li>
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<li>Try to apply the OSM per-lane restrictions ("straight or left" from lane 3)
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<ul>
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<li>The number of lanes in the OSM metadata might not match up with how many
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lanes created</li>
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<li>Some of these OSM tags are just completely wrong sometimes. If the filter
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makes an incoming lane lose all of its turns, then ignore that tag.</li>
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</ul>
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</li>
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</ul>
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</li>
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<li><code>make/parking_blackholes.rs</code>: Find well-connected roads near "blackhole"
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lanes.
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<ul>
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<li>Starting from most driving/biking lanes, most other lanes are reachable.
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Some aren't -- such as one-way highways inevitably leading from or to a
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border. These are "blackholes" -- pathfinding to or from here may fail.</li>
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<li>Find the largest strongly-connected component (SCC) in the driving graph.
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From every other lane (a blackhole), floodfill both forwards and backwards
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to find the nearest driving lane part of the main SCC.</li>
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<li>Later, if a car needs to park by a building on a blackhole road, it'll
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instead start searching for parking at the redirect. This prevents it from
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being forced to instead exit the map through a border.</li>
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</ul>
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</li>
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<li><code>make/buildings.rs</code>: Match buildings up with sidewalks
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<ul>
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<li>Find the closest sidewalk polyline to each building's center. Then draw a
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straight line for the front path between the edge of the building and the
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sidewalk point.</li>
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<li>Filter out buildings too far away from any sidewalk</li>
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<li>The front path might cross through other buildings; this is probably not
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worth fixing.</li>
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</ul>
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</li>
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<li><code>make/buildings.rs</code>: Same for parking lots
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<ul>
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<li>Similar process to match parking lots to nearest sidewalk and driving lane</li>
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<li>Try to place parking spots along both sides of parking aisles</li>
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<li>Filter out overlapping spots</li>
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</ul>
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</li>
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<li><code>make/bridges.rs</code>: Find what roads lie beneath bridges, and update their
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Z-order accordingly for later drawing.</li>
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<li><code>stop_signs.rs</code>: Instantiate default stop sign policies
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<ul>
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<li>Rank incoming roads by OSM priority (arterial beats residential)</li>
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<li>If there's only one rank, then make an all-way stop</li>
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<li>Otherwise, the highest rank gets priority and others stop
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<ul>
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<li>Check if there are any conflicts based on this. If so, then fall-back to
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an all way stop.</li>
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</ul>
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</li>
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</ul>
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</li>
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<li><code>traffic_signals.rs</code>: Instantiate default traffic signal policies
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<ul>
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<li>Apply the first predefined policy that works.
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<ul>
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<li>4-way 4 stage, 4-way 2 stage, 3-way 3-stage, degenerate policy for 2
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roads, 2-stage for 4 one-ways</li>
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<li>Fallback to a greedy assignment that just randomly starts a new stage,
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adds all compatible turns, and repeats until all turns are present
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priority in some stage.</li>
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</ul>
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</li>
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</ul>
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</li>
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<li><code>pathfind/mod.rs</code>: Prepare pathfinding
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<ul>
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<li>A/B Street uses contraction hierarchies (CH) for fast routing, using the
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<code>fast_paths</code> crate.</li>
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<li><code>pathfind/vehicle.rs</code>: For cars, bikes, buses
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<ul>
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<li>There's a separate CH for cars, buses, and bikes, since they can use
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|
slightly different sets of lanes.</li>
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<li>Building the CH for buses and bikes is much faster than the one for cars,
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|
because the algorithm can re-use the node ordering from the first CH.</li>
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<li>Every lane is a node in the graph, even if it's not an appropriate lane
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|
type -- it might change later, and reusing orderings is vital for speed.</li>
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<li>If two lanes are connected by a turn, then there's an edge in the graph.
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<ul>
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<li>The edge weight is the length of the lane and turn. Later this could
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|
take into account speed limit, penalize lane-changing and left turns,
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|
etc.</li>
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</ul>
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</li>
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</ul>
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</li>
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<li><code>pathfind/walking.rs</code>: For pedestrians
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<ul>
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<li>Only sidewalk lanes are nodes in the graph -- sidewalks can't ever be
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|
changed in A/B Street, so there's no concern about reusing node orderings.</li>
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|
<li>All turns between two sidewalks become edges, again using length</li>
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<li>When actually pathfinding, we get back a list of sidewalks. The actual
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|
paths used in the traffic simulation specify forwards or backwards on a
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sidewalk. Looking at adjacent pairs of sidewalks lets us easily stitch
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|
together exact directions.</li>
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</ul>
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</li>
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</ul>
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</li>
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<li><code>make/bus_stops.rs</code>: Match bus stops with a sidewalk
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<ul>
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<li>Also precompute the position where the bus stops on the adjacent driving or
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bus lane.</li>
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|
<li>This "equivalent position on another lane" process has a few weird cases,
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|
since two lanes on the same road might have different lengths. Right now,
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|
the same distance from the start of the lane is used, with clamping for
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shorter lanes. Ideally, the position would be found by projecting a
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|
perpendicular line out from one lane to the other.</li>
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</ul>
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</li>
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<li><code>make/bus_stops.rs</code>: Finalize the list of bus routes
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<ul>
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<li>Between each pair of adjacent bus stops, run pathfinding to verify there's
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actually a path for the bus to follow. If any are disconnected, remove the
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bus route</li>
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<li>Remove bus stops that have no routes serving them.</li>
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</ul>
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</li>
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<li><code>pathfind/walking.rs</code>: Precompute the CH for pedestrians who will use buses
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<ul>
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<li>Nodes in the graph are sidewalks and every bus stop</li>
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<li>There's an edge with weight 0 between a bus stop and its sidewalk</li>
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<li>There's also an edge with weight 0 between bus stops that're adjacent via
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some route. Ideally this weight would account for the time until the next
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bus and the time spent on the bus, etc.</li>
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<li>Later when figuring out which bus to use for a pedestrian, the resulting
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list of nodes is scanned for the first and last bus stop along the same
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route.</li>
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</ul>
|
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</li>
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</ul>
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