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This article looks at the identification of public transport routes that tend to have recurring delays.
Image Source: Adrien Aletti
Expectations vs reality
The fact that passengers really value public transport punctuality makes addressing public transport delays crucial.
A public transport delay refers to a slower or later than expected arrival of a transport vehicle.
Several studies regarding the reception of delays in public transport have found the following results:
- On-time performance (arriving or departing within 5 minutes) is among the most common measures of service reliability for public transport.
- UK train passengers consider a train’s arrival within 1 minute as “on time”. For them, a short-distance train coming 10 minutes later and a long-distance train coming 20 minutes later are “significantly late”.
- UK bus passengers can tolerate missing high-frequency buses but not as much for low-frequency buses.
- UK bus passengers who take the bus to go to work are less tolerant of delays.
- Czech passengers are really okay with waiting for 3 minutes, a little okay with 6 minutes, neutral with 10 minutes and not okay with longer than 10 minutes.
- Even in Malaysia, where absolute punctuality is a myth in Malaysian society, passengers have so much to say about the unreliability of local bus services, which caused many of them to switch to driving their own cars.
- Covid-19 may have reduced public transport delays as data from Deutsche Bahn has shown that its trains were the most punctual in 2020 after 15 years.
Implications of recurring delays, or worse, cancellations
According to a 2013 Passenger Focus report titled “Bus passengers’ experience of delays and disruption” (yes, it’s old but still relevant), passengers are aware that some delays are hard to avoid since buses share road space with other private vehicles and, thus, can get stuck in traffic jams.
However, being able to use the train on time or at all is still a big deal for public transport passengers. The inability to do so can lead to several issues that are deemed unacceptable:
The most obvious implication of delays is lateness. In the Passenger Focus report, the passengers recounted their experiences of delayed bus arrivals leading to missing important appointments, being late to work and being late to their family gatherings.
And since nobody wants to be late, passengers often feel anxious and uncomfortable when they wait for too long, especially if there’s no real-time information of the estimated arrival time.
They wouldn’t know whether to continue tolerating the unpleasant weather or the lack of safety at the bus stop or to book a taxi ride as an alternative transport mode. Such pain of delays cut deeper in multimodal transport routes, which are already time-consuming from the additional waiting time, slowed down vehicle journeys and connection transfers.
What if the later buses are more crowded? What if the passengers miss the earlier connected train rides after their delayed bus rides? What if the passengers have to pay more money as a result of the delays?
Apart from delays being “a poor value of money”, passengers may have to pay for another ticket if the original ticket cannot be used for a later ride or pay a penalty for being late to work. Or they’ll have to pay for a taxi if they decide to book one.
“There’s always anxiety if the last bus is late, you get the last bus or it’s a £30 taxi.”
One UK bus passenger told Passenger Focus.
Not only is the cost of recurring delays higher for passengers, but it is also higher for public transport operators. Public transport operators will have to pay overtime compensation to the transport staff, fare refunds for delayed passengers and contractual fines to the authority if any.
Apart from the higher financial costs for public transport operators, all the issues above should matter to the operators because of the subsequent avoidance of public transport, which reduces revenue in the long run. Passengers, especially the special needs passengers, will be so disillusioned by the quality of public transport that they’ll question its worth and may decide to stop using public transport.
Causes of recurring delays of certain routes
Before we look for solutions to this problem, let’s get to the bottom of it.
What are the common causes of public transport delays?
Generally, the common causes of public transport delays include:
- peak traffic conditions and long bus routes causing arrival delays for buses.
- headway instability because vehicles move faster or slower than expected.
- major events like sports matches and parades influence the speed, headway and crowding levels.
It turns out that there are 2 types of disruptions that cause delays: Expected and Random.
- Examples of expected disruptions: Road closures due to planned roadworks and major events, as well as peak hour traffic jams.
- Examples of random disruptions: Bad weather, breakdowns, road accidents and traffic jams.
Seeing that traffic jams are responsible for bus delays, there are also 2 types of traffic jams: Recurring and non-recurring.
- Recurring: Predictable and repetitive traffic jams due to peak hours.
- Non-recurring: Unexpected and occasional traffic jams due to random disruptions.
Using data to avoid routes with recurring delays and even cancellations
In addition to analysing the demand for certain routes, the routes with regular delays and cancellations also need to be considered in transport planning and operations. We can start finding such routes by identifying patterns of recurring delays and creating recurring delay estimates out of these patterns.
At the same time, routes with recurring delays can be traced to the disruptions causing recurring delays, as done by Tahmasseby, van Nes and van Oort in their 2009 paper titled “Reliability Assessment of Urban Rail Transit Networks; Methodology and Case Study“.
Using a stochastic assessment model to study the tram network in The Hague, they found that long lines and terminal nodes were more vulnerable to disruptions than short lines and non-terminal nodes.
Six years later, Bruglieri, Bruschi, Colorni, Lue, Nocerino and Rana developed MOTUS (Mobility and Tourism in Urban Scenarios), A Real-time Information System for Public Transport in Case of Delays and Service Disruptions based on GTFS, to help divert passengers when there are transport disruptions in the Italian city of Milan.
Similar to Google Transit and Moovit, MOTUS can model so many possibilities of disruptions such as a passenger searching for a route that avoids a temporarily closed station and then propose alternative paths to avoid the closed station.
Image Source: Ben Wicks
Fast forward to 2018, Qingru Zou, Xiangming Yao, Peng Zhao, Fei Dou and Taoyuan Yang recommended Managing Recurrent Congestion of Subway Network in Peak Hours with [the] Station Inflow Control (SIC) method using a bottleneck elimination strategy-based algorithm. This SIC method was built step-by-step:
“First, a traffic assignment model without capacity constraint is utilized to determine passenger flow distributions on the network. An internal relationship between station inflows and section flows is then constructed.
Second, capacity bottlenecks are identified by considering the transport capacity of each section.
Then, a feedback-based bottleneck elimination strategy is established to search target control stations and determine their control time and control strength.”
Managing Recurrent Congestion of Subway Network in Peak Hours with Station Inflow Control (2018)
Based on their findings, the research team concluded that the static SIC method can be used to manage recurring congestion during peak hours because of the subway system’s stability but also warned about sudden congestion pattern changes due to random disruptions.
Managing recurring delays
The first important thing to do to manage recurring delays or disruptions and, thus, improve overall public transport reliability is for transport planners to study the causes of disruptions (both expected and random) and create backup routing paths like splits, detours, shortcuts and turns.
Many measures for managing delays have been suggested in detail by Passenger Focus (page 33), but here’s a summarised version of them to take away for this topic of discussion:
- Provide real-time data about delays and disruptions to minimise anxiety from waiting and allow passengers to divert.
- Execute staggered roadworks instead of blocking the whole road.
- Allow for peak hour adjustments in the schedules by increasing the frequency of vehicles, especially since mass boarding can slow down the departure of vehicles.
- Create bus-only or bus-priority lanes.
- Provide backup vehicles quickly if the expected vehicle is not working and make sure vehicles are well-maintained.
- Provide better shelters at bus stops to minimise the discomfort from waiting.
- Make sure bus drivers can communicate effectively with passengers.
- Provide better customer service teams.