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Conveyal Analysis

1,446 bytes added, 22:19, 31 August 2017
edits for update to Conveyal Analysis
|title=Transport AnalystConveyal Analysis
|data_in= [[GTFS]], [[OpenStreetMap]], ACS/Census, LODES, custom shapefiles
|data_out= GIS shapefiles, maps, accessibility graphs, GeoTIFF,
|website= []
Transport Analyst Conveyal Analysis integrates transit and land use data to compare current system performance and accessibility with various scenarios. It is an open source tool developed by [[Conveyal]], and can be hosted and run independently or hosted by Conveyal for a fee along with consulting services.
==Accessibility Assessment==
[[File:Conveyal-jobs-access.png|thumb|Identifying places that see increased access to jobs due to a new transit line. <br>Source:]]
[[File:Analysis-spectrogram.png|thumb|Accessibility spectrogram from Conveyal Analyst. Shows the increase in accessible opportunities (in this case jobs) as travel time increases. The wider portions reveal system uncertainty or unreliability caused by low service frequency.<ref>Conveyal analysis-ui documentation. Accessed 20 April 2017.</ref> ]]
Analyst Conveyal Analysis offers basic statistics of how far or fast a system can carry people but also, by layering information from [[OpenStreetMap]] and census data, it allows planners to view accessibility. Analyst It can display job opportunities, businesses, and various amenities that become more accessible to people living near a new planned transit line. Accessibility outcomes offer new opportunities for collaboration between land use and transportation planning. The software can intake multiple alternatives and return graphical prototypes such as spectrograms stacked percentile plots and histograms isochrones that compare accessibility outcomes for the different scenarios.
The accessibility outcomes offered by Analyst display the total number of a given amenity that can be reached within a given amount of Conveyal Analysis measures travel time from a given point, or for a full system analysis, the number of origin destination combinations available as multiple iteration within a given amount of travel timewindow. For example, it can show how many jobs can be reached from a householdif the time window is set to 7am to 9am, Conveyal will check accessible destinations at 7am, 7:01, or how many household-job combinations exist withing a time cutoff7:02 etc. The information is displayed as a spectrogram that demonstrates the change in access number of trips to fit into the given amenity as the travel time cutoff increases, and as a histogram that shows the variability of accessibility for a given time cutoff with in a time range, highlighting window can be set by the effects of schedules and headwaysuser.
===Single point analysis===
[[File:Conveyal-isochrone.png|thumb|Two isochrones are shown for a baseline and project scenario, demonstrating travel accessibility in a 45 minute time window <ref>Analysis-Conveyal Accessed Aug 31 2017</ref>]]
[[File:Conveyal-comparison.png|thumb|Shows the stacked percentile curves, indicating access to jobs and reliability for a baseline and scenario case<ref>Analysis-Conveyal Accessed Aug 31 2017</ref>]]
The accessibility outcomes offered by Conveyal Analysis display the total number of a given amenity that can be reached within a given amount of time from a given point or within a region. For point analysis, accessibility can be viewed as an isochrone, showing how far someone could get on a map within a certain travel time budget. The data is also presented as a stacked percentile plot. The curve reveals how many opportunities are available as the median travel time increases or decreases. The stacked percentiles show the extent to which accessible destinations change depending on the time of departure. A wide spread indicates lower reliability, that is, many destinations are only accessible within a travel time budget when leaving at a specified time.
===Regional Analysis===
[[File:Conveyal-regional|thumb|A map showing the relative opportunities to jobs for the Atlanta region <ref>Conveyal analysis Docs Accessed Aug 31 2017</ref>]]
Regional analysis calculates all of the accessible connections between households and jobs, or another destination, within the region. These are based on a predetermined time cut-off. By default, the user can choose the median travel time. However, if the user is interested in transportation for shopping trips, which may have more flexible arrival times, or for employment or school, which often have rigid arrival times, the user can choose a certain percentile above or below the median travel time. The results are displayed in on a map with a color scheme based on the number of opportunities at each grid cell.
Conveyal does not use [[TAZ]]s, which are commonly employed, but rather a fine grid, resulting in more granular data quality of accessibility.
A single point analysis, showing accessibility from that point to all other points, can be calculated quickly, usually taking 5-15 second. An analysis of an entire region, looking at accessibility from every point to every other point, takes longer. The factors that most affect computation time are the size of the region, the number of points in the region, and the size and density of the transit and transportation network. Furthermore, a scenario analysis is able to use results from the base case and only run the analysis where results will differ. Therefore, more changes in a scenario will lead to longer computational time. An analysis run on a single server can take anywhere from a few hours to a few days depending on the complexity of the system. If the analysis is run on multiple servers, either using [[Conveyal|Conveyal's]] hosting service or through other access to cluster computing, the runtime can be reduced to a few minutes to a few hours.
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