Measuring Travel Time Reliability for an FCD-based Route Information System

Size: px

Start display at page:

Download "Measuring Travel Time Reliability for an FCD-based Route Information System"

Adam Hubbard
8 years ago
Views:

Rüdiger Ebendt Measuring TTR for an > 08

1 Measuring Travel Time Reliability for an FCD-based Route Information System Rüdiger Ebendt Measuring TTR for an FCD-based Route Information System > 08 October 2012 > 1

2 German Aerospace Center Exploratory Focuses Aeronautics Space Transport Energy Safety Funding 2009: Mio. Euro 2010: Mio. Euro 6,200 employees working in 29 research institutes and facilities at 13 sites. Measuring TTR for an FCD-based Route Information System > 08 October 2012 > 2

3 Transportation Participating institutes Institute of Transport Research Project Transport Studies Hamburg Bremen- Neustrelitz Trauen Berlin- Braunschweig Göttingen Institute of Transportation Systems Köln Bonn Institute of Vehicle Concepts and 21 more institutes from aeronautics, space and energy Lampoldshausen Stuttgart Oberpfaffenhofen Weilheim Measuring TTR for an FCD-based Route Information System > 08 October 2012 > 3

4 Institute of Transportation Systems Residence: Since: March 2001 Director: Employees: Range of tasks Basic research Braunschweig and Berlin Prof. Dr.-Ing. Karsten Lemmer Presently 100 employees from various scientific disciplines Creating concepts and strategies Prototype development Fields of Research Automotive Railway Systems Traffic Management Measuring TTR for an FCD-based Route Information System > 08 October 2012 > 4

5 Scope and Outline of the Talk Travel Time Reliability (TTR) is usually used as a performance indicator of a road network or of the service provided to the driver TTR is usually used offline Here, we consider a particular service of a traveller s information system: a continuous route monitoring in VABENE We will focus on the FCD-based estimates computed for this purpose A TTR-based measure is suggested for assessment of the service quality It has been deployed for Cologne/Bonn, Germany, and it continuously assesses the reliability of the route monitoring service (1 value for each hour) This works by using the actual travel times of probe vehicles (taxis) as a ground truth Self-evaluation Measuring TTR for an FCD-based Route Information System > 08 October 2012 > 5

6 Route Monitoring in VABENE (Cologne/Bonn) Measuring TTR for an FCD-based Route Information System > 08 October 2012 > 6

7 Floating Car Data (FCD) Travel time or travel speed (t 2, x 2 ) (t 1, x 1 ) Measuring TTR for an FCD-based Route Information System > 08 October 2012 > 7

8 Reisezeit [Minuten] Floating Car Data (FCD) Several vehicles: Mean travel time or travel speed on the link, e.g. t 1 n n i 1 ( t ) Historical link travel times (for that particular TOD and DOW, that is, for every link and for every of the 168 hours of the week) used for enrichment Tagesgang Route 1-1 (by Time) where current FCD is scarce i Reisezeiten Einzelfahrzeuge Tagesgang (Durchschnitt) Tagesgang min Tagesgang max Basis-Reisezeit Gelb Rot Tageszeit [h] Measuring TTR for an FCD-based Route Information System > 08 October 2012 > 8

9 Link-based vs. Actual Route Travel Times Measuring TTR for an FCD-based Route Information System > 08 October 2012 > 9

10 Self-Evaluation: Accuracy x x ref def t X def X t t R R t. x xref e sys 100 % x ref Measuring TTR for an FCD-based Route Information System > 08 October 2012 > 10

11 Self-Validation: Reliability Berlin: self-evaluation of accuracy instead of field tests For this purpose, the tracking data of the probe vehicles was used offline Cologne/Bonn (VABENE): a continuous self-evaluation of accuracy and reliability Reliability : Travel Time Reliability, service reliability (route monitoring) Measuring TTR for an FCD-based Route Information System > 08 October 2012 > 11

12 Travel Time Reliability (TTR) Travel time reliability depends on both the variability and the stability of the traffic (see e.g. Tu, 2008). Measures proposed in the past: Expressed as travel times themselves, e.g. as the extra travel time a traveler is advised to include, in order to arrive in time Probabilistic measures which consider the probability that a trip will be made within the nominal travel time, multiplied by a certain factor Skew-width measures which consider the skew of the travel time distribution, usually using percentile-based definitions (e.g. ratios of percentile distances) Measuring TTR for an FCD-based Route Information System > 08 October 2012 > 12

13 TTR: Probabilistic Measures Measuring TTR for an FCD-based Route Information System > 08 October 2012 > 13

14 FDOT-Reliability Measuring TTR for an FCD-based Route Information System > 08 October 2012 > 14

15 Link vs. Path-Based Measures for travel time or speed on predefined routes: link-based: as the sum of FCD average travel times for the constituting links Disadvantages: does not reflect all delays caused by e.g. left-turns on a signalized intersection has the tendency of propagating the variance of the travel time on the path, due to correlations between (neighbored) links Measuring TTR for an FCD-based Route Information System > 08 October 2012 > 15

16 Link vs. Path-Based Measures Therefore: path-based: use actual travel times of individual vehicles with trajectories (partly) along the route Measuring TTR for an FCD-based Route Information System > 08 October 2012 > 16

17 Link vs. Path-Based Measures Measuring TTR for an FCD-based Route Information System > 08 October 2012 > 17

18 Combining Link- and Path-based Measures Measuring TTR for an FCD-based Route Information System > 08 October 2012 > 18

19 Combining Link- and Path-based Measures Measuring TTR for an FCD-based Route Information System > 08 October 2012 > 19

20 Reliability of the Route Monitoring Service A TTR measure like FDOT (Florida) reliability depends on the variability of traffic Question: How reliable are the monitored estimates? This depends both on the (variability of) traffic, and on how reliably the monitor reproduces the actual travel times Nonetheless, FDOT reliability could be used as a measure for the monitor Measuring TTR for an FCD-based Route Information System > 08 October 2012 > 20

21 Reliability of the Route Monitoring Service Problems: Online system, much shorter time periods are considered Therefore much less data Monitor estimates are updated every ten minutes We would have to compare estimate to travel times that occurred within the current time slice of ten minutes Perhaps too short, too few trajectories, statistics may not be sufficient! If this is not the case: good, FDOT reliability is a possible measure (Berlin: taxis, works, but what about Cologne/Bonn: 320 taxis?) Measuring TTR for an FCD-based Route Information System > 08 October 2012 > 21

22 Reliability of the Route Monitoring Service Measuring TTR for an FCD-based Route Information System > 08 October 2012 > 22

23 Reliability (%) Reliability (%) Experiments: German Unification Day 2011 Taxi traffic FCD system Impr. monitor 00:00-01:00 05:00-06:00 10:00-11:00 15:00-16:00 20:00-21:00 Time of Day Estimates were not significantly less reliable than the actual (observed) traffic itself Sometimes even more reliable Taxi traffic FCD system Combined 00:00-01:00 05:00-06:00 10:00-11:00 15:00-16:00 20:00-21:00 Time of Day Measuring TTR for an FCD-based Route Information System > 08 October 2012 > 23

24 Conclusions Idea of online "self-evaluation": Individual actual travel times are used as "ground truth to continuously assess the reliability of an FCD-based route monitoring system A probability-based measure for TTR was used Result for Cologne/Bonn: Most of the time, the route monitor had a reliability between 80% and 100%, that is, it was not significantly less reliable than the actual traffic itself sometimes it was even more reliable (due to the use of historical patterns) Measuring TTR for an FCD-based Route Information System > 08 October 2012 > 24

25 Thank you for your attention! (030) Deutsches Zentrum für Luft- und Raumfahrt e.v. (DLR) Institut für Verkehrssystemtechnik Rutherfordstraße Berlin Measuring TTR for an FCD-based Route Information System > 08 October 2012 > 25

Doctoral degree scholarship. in aeronautics and space travel technology

Doctoral degree scholarship. in aeronautics and space travel technology Doctoral degree scholarship in aeronautics and space travel technology Scholarship program Munich Aerospace grants scholarships to support young scientists in their doctoral studies. The scholarships are