Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE credits
One of the main objectives of public transport operators is to adhere to the planned timetable
and to provide accurate information to passengers in order to improve actual and perceived
service reliability. The aim of this thesis is to address the flowing question: how can the
accuracy of a prediction system for light rail systems be measured and improved?
The real-time prediction is an output of a telecommunication system, named Automatic
Vehicle Location System, which computerizes the predictions. In order to improve a system, it is
first important to understand how it works. The mechanism of the prediction computation will be
analyzed and each part of the process will be studied in order to seek potential improvements.
The first part of the prediction scheme development consists in a statistical analysis of historical
data to provide the reference travel times and dwell times and their variations along a day or
along a week. Then, two models (the designed-speed model and the speed/position model) will
be studied to estimate the remaining time to reach the downstream stop. This estimation is
mainly based on the current data (vehicle position and speed).
The proposed prediction schemes were implemented and applied for a case study light rail
line. Bybanen, a light rail train in Bergen was selected as case study. Real-time information
displays are available at all platforms and refer to the waiting to the next two light rail trains.
This study focuses on improving the accuracy of these waiting times predictions.
In order to establish and analyze the performance of the current prediction scheme, a model
for reproducing these computations was developed. Then, the possible improvements have
been implemented in the model and the accuracy of the new predictions has been compared to
the base case. The assessment and the comparison of prediction systems are not trivial tasks.
Which predictions should be taken into account? How does the model identify inconsistency in
the data? How could the perception of passengers be taken into account?
A set of measures has been used in order to evaluate alternative prediction schemes. The
comparison of the different models shows that it is possible to improve the accuracy of the
short-term predictions, but it is more difficult to improve the accuracy of long-term predictions
because the incertitude of small changes has more impact in long-term predictions. This thesis
shows that the reference travel times and dwell times should be assimilated to the most
common value instead of the average which is too dependent on high values. Moreover, the
dwell time variations are related to the flow passengers. Finally, the most accurate and efficient
model is the designed-speed model. The speed/position model is a bit less accurate except in
the case of disturbances along the line but its modularity made easier possible improvements.
Finally, this paper highlights the time-depending variations of the dwell time in the case of a
light rail train system. It could be interesting to analyze the behavior of variations of two
consequent dwell times and to implement a forgetting factor. Moreover, the speed-position
model shows really good results and a better understanding of the drivers’ behaviors is a key to
improve the model. Finally, the differences between the different models will be probably larger
for a middle-distance train system, which could be an interesting application of this thesis.
2014. , 94 p.