DRT or Bus?
Financial constraints often dictate public transport planning. Buses are effective in high density areas, but it becomes difficult to provide a quality service in a cost effective manner is lower density areas. Demand responsive transport may offer another tool to provide a high quality service in these areas and potentially cost savings by removing particularly poorly performing bus routes.
The goal of this post is to explain initial methods of exploring bus/DRT network redundancy in Logan, QLD and to identify potential bus routes for replacement based on observed behavioral preferences. Throughout this post, bus frequency is used as a proxy for service provision. This limitation is less pronounced than in most trip modelling as DRT frequently serves similar hubs as the bus network.
The Logan DRT trial uses a fixed attractor model which allows for users to register their home address to gain service to local transport, health, and shopping hubs. DRT was intentionally planned to provide services outside of the normal bus network.
From a financial perspective, service success is reliant on providing low cost, shared trips. Longer trips cost more to provide, and design of the network is important in shaping these behaviors.
Without exploring individuals’ personal behavior, the following work demonstrates DRT usage based on bus frequency. Throughout this post, buses per hour are used, segmented into places with no bus service (white), between zero and three buses per hour (yellow), and more than 3 buses per hour (green). Each bus stop has been modeled in using a 400m buffer distance along the road network to simulate bus catchments.
Are people using DRT instead of the bus?
Providing redundant services increases system cost and decreases efficiency by cannibalizing demand on routes. The goal of this DRT trial was to provide services to areas without public transport service, thus presenting a key performance indicator.
This section examines DRT trips that take place with home locations in high frequency bus catchments. These trips represent 4% (~1,400)of the total trips on the network, and unsurprisingly is limited in the more rural areas found in Zone A (twenty trips). Zone C held 1,000 of these trips, while Zone B held 400.
Due to the high volume of bus routes and the limited DRT demand in these areas, there were no clear and obvious bus routes that could be identified for potential removal.
These trips were undertaken by a small number of individuals (57), and the ten most frequent riders represented 74% of all of the trips taken. This small number represents a feasible size for personalized contact for future research and could offer insights into why they aren’t using the bus.
The limited volume (4%) of redundant trips is reassuring, and does not suggest a need to impact DRT services. This number should be monitored in case it grows, and should be used as a benchmark for future service planning.
Can we replace some low performing bus routes with DRT?
If DRT is providing a useful service, maybe it can be used to
This section examines DRT trips that take place with home locations in low frequency bus catchments, between zero and three buses per hour. These trips represent 22% (~8,500)of the total trips on the network, and is split throughout the zones following general DRT usage patterns. Zone A had 4,590 trips, Zone B had 2,600, and Zone C 1,380.
Based on these differences in trip volumes and the limited findings from the redundancy analysis, distribution of trip distance was evaluated. The findings demonstrated that the larger zone, Zone A, had a much longer trips which could be attributed to two different attractor areas.
Zone A’s main attractors were Grand Plaza with 2,283 trips, Loganlea Train with 1,151 trips, and Logan Hospital with 406 trips. Loganlea Train and Logan Hospital are quite proximal, and were combined in this analysis.
Loganlea Train and Logan Hospital
Trips to Loganlea Train station and Logan Hospital represent around 33% of the trips in Zone A (1,500 trips) and were on average 18km. These trips clearly represent the upper clump of the trip distances and are partially responsible for the higher trip lengths in Zone A.
DRT usage centered in Bornonia Heights on the left side of the map. Service to the hospital and train station is limited to the 560 bus route shown in blue. To access these locations takes around 40 minutes on the 560 from the start of the route, requiring that these DRT users would need to transfer from their local bus (which runs once or twice an hour).
DRT users take a completely different route, going north to Logan Motorway, a drive which takes around 10 minutes. There should be no surprise in this instance which method of transport is used.
Grand Plaza
The Grand Plaza attractor had 2,200 trips, most from the same area in Boronia Heights as the Loganlea attractors. While many of the trips took place on the bus network, limited bus frequency and longer trip times may have resulted in users preferring to use DRT.
Most of the trips took place on routes 541 and 542, and these routes serve as potential routes that could be replaced with DRT. Both of these routes run at 30 minute intervals during peak hours and hourly intervals during off peak and weekends with operations between 6am and 7pm. DRT could be used as a full replacement or to supplement current hours. Further exploration into when users book DRT trips will provide a better understanding of if these trips are occurring during bus hours of operation.
4 Initial Conclusions
- Planning drives behavior: In this form of DRT provision, the location of attractors and the size of zones determines how people act. It should come as no surprise that there are longer trips in Zone A as the zone is large and attractors are located on a fringe.
- DRT may serve to replace certain routes: in some instances, DRT users are preferring to ride DRT even when there is a bus. Low frequency areas offer potential bus replacements or service adjustment with DRT.
- In this trial, there is a very small number of DRT trips occurring in areas with high bus frequency. This should be used as a key performance indicator when planning and evaluating DRT services.
- The majority of trips (around 70%) in this trial are in areas with no bus service. This should also be used as a key performance indicator moving forward.
