Speed Map Basics

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The Speed Map module visualizes the average travel speed for a route in a given direction for either stop-to-stop segments or smaller "high-resolution" segments. This can be used to identify where planning efforts should be focused on by identifying streets with slow travel and stops with high dwell times and might be candidates for additional infrastructure investment.

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Video Overview

The basics

Overview: View your agency's historical route speed information for multiple segment lengths.  With a flexible interface and color-coded speeds, this module helps you understand where slowdowns occur on your routes or quickly pinpoint high dwell times at certain stops.  

Filters: In the Speed Map module you can focus on a specific route's speed data. You can also look at performance for a single day or over a longer date range, as well as exclude any particular dates that may impact on-time performance (snow days, events that disrupt service, etc.). 

In the Speed Map module, you can adjust how long of a segment we display speed information:

  • High-Resolution Speeds: Get speed information for approximately 25m long segments on your route. 
  • Stop-to-Stop Speeds: Get speed information for stop-to-stop segments. 

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Edit the Speed Legend – From the left-hand filters panel, select Display to edit the speed legend. This will allow you to edit the "buckets" that are color-coded on the Speed Map.

 
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Visualize slow segments – The slower the segment, the more red the segment line will be. Check the Legend at the bottom of the screen for reference. Click on any segment to reveal more detailed information about average speed and the number of recorded trips. Zoom in closer to view the average speed by segment displayed right on the map. 

 

Spot high dwell points – Zoom in closer on the map to view route stops, represented by circles sized by average dwell time; Larger circles mean longer average dwell time, smaller ones mean shorter average dwell time. Click on a stop to reveal more detailed information, like the specific average dwell time, and the number of recorded trips counted. Note: in the high-resolution display option, dwell time is included in segment speed, but it is separated in stop-to-stop view. This means that you'll notice slower speed near stops due to time slowing down, waiting at a stop, and leaving a stop.

 

Speed Estimation Methodology

Stop-to-stops speeds are calculated using stop-level estimates of when a vehicle arrived and departed a stop. The time spent traveling from one stop to the next is determined by using the estimated departure time from the prior stop and the estimated arrival time to the subsequent stop. This information is based on vehicle location data and does not include time spent at a stop ("dwell"). To calculate speed, which is distance over time, the distance is specified in GTFS and is divided by the observed travel times. 

Dwell times in stop-to-stop speeds are calculated using the difference in departure time and arrival time at a given stop.

High-resolution speeds are derived directly from the vehicle location data and where along the route path the vehicle is most likely to be using our spatial and temporal "matching" algorithm. Sequential observations and the implied speed based on the distance between vehicle location observations and the gap in time are then used to estimate speeds that fall within segments of up to 25 meters. Actual segments may be shorter when the distances between stops do not cleanly break into 25-meter segments. Instead, we will provide information in equally-sized segments. Time spent slowing down towards, dwelling at, and speeding up from a stop is incorporated into the segments closest to stops, so you'll notice slower speeds around stops. 

The accuracy of Swiftly's speeds is a function of the underlying data. When vehicle location data is infrequent, such as only every 30 seconds, speed data, particularly for shorter segments, may be less accurate as a vehicle can traverse multiple stops between GPS pings. Additionally, speeds data may be inaccurate if the location of the stop in the GTFS shape is not where the vehicle actually stops.

Speeds data is sometimes not available, such as when there is an insufficient sample size. Consider increasing your date & time range to increase sample size or switch to High Resolution Speeds instead.

 

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