abstreet/how_it_works.html
2020-09-04 01:05:10 +00:00

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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" class="active"><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"><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></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="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></ol></li></ol>
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<h1 class="menu-title">A/B Street</h1>
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<h1><a class="header" href="#how-ab-street-works" id="how-ab-street-works">How A/B Street works</a></h1>
<p>The overview:</p>
<ol>
<li>A detailed map of Seattle is built from
<a href="https://www.openstreetmap.org/about">OpenStreetMap (OSM)</a></li>
<li>A realistic set of daily trips by car, bike, foot, and bus are simulated</li>
<li>You make small changes to roads and intersections</li>
<li>You explore how these changes affect the trips</li>
</ol>
<p>Details below. Many limitations are mentioned; improvements are ongoing. I'll
add pictures to explain better when I get time.</p>
<!--ts-->
<ul>
<li><a href="#how-ab-street-works">How A/B Street works</a>
<ul>
<li><a href="#driving">Driving</a></li>
<li><a href="#parking">Parking</a></li>
<li><a href="#biking">Biking</a></li>
<li><a href="#walking">Walking</a></li>
<li><a href="#transit">Transit</a></li>
<li><a href="#intersections">Intersections</a></li>
<li><a href="#people-and-trips">People and trips</a></li>
<li><a href="#map-edits">Map edits</a></li>
</ul>
</li>
</ul>
<!-- Added by: dabreegster, at: Mon Jun 8 12:17:13 PDT 2020 -->
<!--te-->
<h2><a class="header" href="#driving" id="driving">Driving</a></h2>
<ul>
<li>Movement: no acceleration, go the full speed limit of the road unless there's
a slower vehicle in front</li>
<li>Lanes
<ul>
<li>No over-taking or lane-changing in the middle of a road, only at
intersections</li>
<li>Strange choice of lanes -- the least full at the time of arrival</li>
<li>Narrow two-way neighborhood roads where, in practice, only one car at a time
can go are currently full two-way roads</li>
</ul>
</li>
<li>Routing is based on fastest time assuming no traffic
<ul>
<li>No rerouting if the driver encounters a traffic jam</li>
</ul>
</li>
</ul>
<h2><a class="header" href="#parking" id="parking">Parking</a></h2>
<ul>
<li>Types
<ul>
<li>On-street: parallel parking lanes from
<a href="http://data-seattlecitygis.opendata.arcgis.com/datasets/blockface">GeoData blockface dataset</a>
and
<a href="https://dabreegster.github.io/abstreet/map_parking.html">manually mapped</a></li>
<li>Off-street: most buildings have at least a few parking spots in a driveway
or carport
<ul>
<li>Currently experimenting in the downtown map: set the number of available
spots based on number of cars seeded at midnight</li>
</ul>
</li>
<li>Parking lots: the number of spots is inferred</li>
</ul>
</li>
<li>Restrictions
<ul>
<li>All spots are public except for the few spots associated with each building</li>
<li>No time restrictions or modeling of payment</li>
</ul>
</li>
<li>How cars park
<ul>
<li>Drivers won't look for parking until they first reach their destination
building. Then they'll drive to the nearest open parking spot (magically
knowing what spots are open, even if they're a few blocks away). If somebody
else has taken the spot when they arrive, they'll try again.</li>
<li>Once a driver finds an open spot, they'll take 10-15 seconds to park. They
block the road behind them in the meantime. There are no conflicts between
pedestrians and cars when using a driveway. Cars won't make left turns into
or out of driveways.</li>
</ul>
</li>
<li>Some parking along the boundary of the map is &quot;blackholed&quot;, meaning it's
impossible to actually reach it. Nobody will use these spots.</li>
</ul>
<h2><a class="header" href="#biking" id="biking">Biking</a></h2>
<ul>
<li>Choice of lane
<ul>
<li>Multi-use trails like the Burke Gilman and separated cycle-tracks like the
one along Broadway are currently missing</li>
<li>Cyclists won't use an empty parking lane</li>
<li>On roads without a bike lane, cyclists currently won't stick to the
rightmost lane</li>
<li>No over-taking yet, so cars can get stuck behind a bike even if there's a
passing lane</li>
</ul>
</li>
<li>Elevation change isn't factored into route choice or speed yet; pretend
everybody has an e-bike</li>
<li>Beginning or ending a cycling trip takes 30-45 seconds. Locking up at bike
racks with limited capacity isn't modeled; in practice, it's always easy in
Seattle to find a place to lock up.</li>
</ul>
<h2><a class="header" href="#walking" id="walking">Walking</a></h2>
<ul>
<li>Not using sidewalk and crosswalk data from OSM yet</li>
<li>No jay-walking, even on empty residential streets</li>
<li>Pedestrians can't use roads without sidewalks at all
<ul>
<li>When a road only has a sidewalk on one side, driveways will cross the road</li>
</ul>
</li>
<li>Pedestrians can &quot;ghost&quot; through each other; crowds of people can grow to any
size</li>
</ul>
<h2><a class="header" href="#transit" id="transit">Transit</a></h2>
<ul>
<li>The modeling of buses is extremely simple and buggy; I'll work on this soon</li>
<li>No light rail yet</li>
</ul>
<h2><a class="header" href="#intersections" id="intersections">Intersections</a></h2>
<ul>
<li>Conflicting movements are coarse: a second vehicle won't start a conflicting
turn, even if the first vehicle is physically out of the way but still
partially in the intersection</li>
<li>Most of the time, vehicles won't &quot;block the box&quot; -- if there's no room in the
target lane, a vehicle won't start turning and risk getting stuck in the
intersection</li>
<li>Traffic signals
<ul>
<li>Only fixed timers; no actuated signals or
<a href="https://www.seattle.gov/transportation/projects-and-programs/programs/technology-program/mercer-scoot">centralized control</a>
yet</li>
<li>The timing and stages are automatically guessed, except some intersections
are
<a href="https://docs.google.com/document/d/1Od_7WvBVYsvpY4etRI0sKmYmZnwXMAXcJxVmm8Iwdcg/edit?usp=sharing">manually mapped</a></li>
<li>No pedestrian beg buttons; walk signals always come on</li>
<li>The signal doesn't change for rush hour or weekday/weekend traffic; there's
one pattern all day</li>
</ul>
</li>
<li>Turn restrictions from OSM are applied
<ul>
<li>Per lane (left turn only from leftmost lane), entire roads, multiple
intersections</li>
</ul>
</li>
</ul>
<h2><a class="header" href="#people-and-trips" id="people-and-trips">People and trips</a></h2>
<ul>
<li>A &quot;synthetic population&quot; of ~700,000 people come from
<a href="https://www.psrc.org/activity-based-travel-model-soundcast">PSRC's Soundcast model</a>
<ul>
<li>Soundcast uses census, land-use, vehicle counts, and commuter surveys. The
current data is from 2014.</li>
<li>All driving trips are currently single-occupancy; no car-pooling or
ridesharing</li>
<li>Parked cars are initially placed at midnight based on the number of trips
between buildings</li>
</ul>
</li>
<li>Each person's schedule never changes
<ul>
<li>Your changes to the map won't yet convince somebody to take a bus or walk
instead of drive</li>
</ul>
</li>
</ul>
<h2><a class="header" href="#map-edits" id="map-edits">Map edits</a></h2>
<ul>
<li>Types of edits
<ul>
<li>Change types of lanes. Sometimes this is unrealistic based on actual road
width, but data for this is unavailable.</li>
<li>Reversing direction of lanes</li>
<li>Changing stop signs</li>
<li>Changing traffic signal timing</li>
<li>Closing roads and intersections for construction, forcing rerouting</li>
</ul>
</li>
<li>Disconnecting the map
<ul>
<li>Generally you can't close sidewalks or make changes to make buildings
unreachable</li>
<li>You shouldn't be able to make bus stops unreachable, but currently this is
buggy</li>
</ul>
</li>
</ul>
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