What if we can improve the efficiency of LRT crossings?

Light Rail Transit (LRT) systems have made a major comeback since many cities around the world decided to tear up their tram tracks decades ago. In many Canadian cities, LRT systems are being embraced in order to accommodate trends in rapid population growth and increasing traffic congestion1. However, intersections where LRT systems cross local traffic pose a significant challenge for everyone due to the heightened complexity and safety concerns. The design of at-grade crossings can have major impacts on the overall efficiency and safety of an LRT system, and are more important now than ever before.

Why are LRT crossings so critical?

Traffic congestion is getting worse. Commuters in major cities such as Toronto, Montreal and Vancouver spend an equivalent of 10,000 years stuck in traffic congestion annually2. The annual cost of congestion to commuters in the Greater Toronto and Hamilton Area was $3.3 billion in 2006, and is expected to more than double to $7.8 billion by 20313. There is strong advocacy for public transit, and Light Rail Transit (LRT) has become increasingly popular in recent decades largely due to its cheaper capital and operating costs. It is capable of providing a higher capacity and faster travel speed than surface transit4, allowing passengers to commute more easily and economically.

Many transit authorities are promoting an “Urban Style” LRT which runs at-grade on major road networks, as LRT systems do not require a dedicated right-of-way (ROW) compared to a full-scale Metro system. This design brings numerous benefits5:

  • Promotes integration of neighborhoods without dividing community with physical barriers
  • Street-level stations provide easy access for people with special needs, such as mobility impaired, aging population, and people with strollers
  • Contributes to walkable, connected, and safe communities
  • Stimulates investment and intensification at the intersections and along the line

However, there have also been many controversies about LRT crossings due to concerns regarding cost, safety, delays, and environmental impacts. Frustrations and incidents constantly arise for drivers, cyclists, pedestrians, and LRT operators. Can we improve the design of an LRT crossing to be more efficient?

What crossing technologies are available?

Currently, there is variety of options available for an LRT crossing, including regular audible and visual warning systems (bells and flashing lights), crossing gates, Transit Signal Priority (TSP), and grade separation.

Audible and visual warning signs: Amongst these options, the simplest, most common, and lowest cost is to install bells and flashing lights at the crossing area to warn the traffic and pedestrian flow of an approaching LRT vehicle. This solution can be effective when both rail and traffic volume are low, however it is a “bare-minimum” warning system. While inexpensive to implement, it does not optimize traffic nor LRT flow, and can result in operational and potentially unsafe interferences from pedestrians and cars accidentally entering the LRT right of way.

Crossing Gates: They are often installed for further protection. Transport Canada provides criteria in its Grade Crossing Handbook6 to determine whether crossing gates are required at a railway crossing, with main considerations being speed, traffic, and LRT volume. When implementing a full-preemption strategy, LRT operation is protected by gates and has full priority over vehicular, bicycle, and pedestrian traffic. However, this can be disruptive. According to a City of Edmonton report, a vehicle can spend up to 16 minutes in traffic at crossing gates7 and the GHG emissions produced from cars while idling behind gates could become a major concern to the environment8. An alternative is to apply “soft-preemption”, where the priority of a Light Rail Vehicle (LRV) is determined based on certain criteria such as clearance of the previous train and real-time traffic volume on opposing movements9.

Traffic Signals/Transit Signal Priority: Another way to control an LRT crossing is by using traffic signals, where an LRV is treated as a regular transit vehicle and should obey traffic signals. This method can be combined with TSP which provides an operational strategy to better facilitate the movements of in-service transit vehicles through such intersections. Unlike preemption methods, TSP does not abruptly stop any traffic to fully protect another. Its main objective is to improve transit efficiency and schedule adherence, while minimizing the impact to local traffic10. TSP systems are usually made up of four components: Transit Vehicle Detection System; Request Generator; Priority Control Strategies and Management Software. TSP can be implemented in various ways:

  • Passive priority (serves the transit phase all the time, irrespective of a transit vehicle being present)
  • Active priority (Actively adjusts signal timings based on approaching transit vehicles using techniques such as green extension, early green, actuated transit phases, phase insertion/rotation)
  • Adaptive priority (intakes real-time data from all modes of transportation /requests to determine phase and cycle length for efficient traffic flow)

TSP can be applied unconditionally (always prioritize transit vehicles) or conditionally (only prioritize transit vehicles based on certain criteria, such as a behind-schedule vehicle). TSP can be applied at an isolated intersection, as well as along a major transit corridor where peer-to-peer communications can be used between signal controllers to maximize its benefits. Peer-to-peer communications allow the signal controllers to communicate LRV locations and estimated travel times between intersections. Accompanying any TSP deployment with a traffic signal optimization study will also improve the overall performance of the corridor. A simple TSP presentation for an LRT intersection is shown below.

LRT transit signal priority

Each case could require a different control strategy. Many cities have generally indicated a 15% saving in transit vehicle travel time after implementing TSP, with minor impacts on vehicular traffic11. The effectiveness of a TSP intersection depends on many factors, such as traffic volume, vehicle and pedestrian flow, priority algorithm, detection methods, as well as the location of the transit stops. It has been found that TSP is more effective if the stops are placed far-side (after the intersection)12, since transit vehicles would not be stopped at the intersection after dwelling at the stop, allowing for better prediction of arrival time and schedule adherence. As the intersection is controlled by regular traffic signals, it would promote a connected and integrated community while improving accessibility by eliminating physical barriers and noise from a typical gate crossing system13. Simulations are widely applied to evaluate the impact of TSP14 and many studies are being developed to achieve further improvements.

Grade separation: The LRT is separated from road vehicles and pedestrian traffic by having its own dedicated ROW through an elevated, trenched, or underground structure. All traffic flows involved in this crossing would be well protected and safe. However, the cost to build and the construction time required introduces inefficiency. It could also become a physical wall or barrier separating a neighborhood and it can be challenging to be integrated into the community if it is elevated or trenched, especially in a low-rise dwelling area. This would not be beneficial for building a connected and integrated community15.

What are the concerns with current LRT crossings?

The various LRT crossing technologies aim to create efficient crossings for all modes. However, there are many concerns as illustrated in the next figure.

Concerns with LRT crossings

Safety: Crossing another route at the same grade presents increased risks at the intersection due to the size of LRVs and potential risk of collisions. Aside from grade separation, the prevailing designs include one or more movements stopping at an intersection while other movements proceed. This reduces the risk of collision, but creates additional waiting time for the stopped flow. An effective warning system is critical not only to ensure safety, but also to allow LRT operation to be more efficient, resulting in reduced system delays due to accidents.

LRT Operation and Local Traffic: For an at-grade crossing intersection, one key question is which mode should be prioritized? Applying full pre-emption in favour of transit vehicles could be disruptive to vehicular traffic. While TSP tries to minimize the impact on local traffic, it would not fully ensure LRV travel times like full pre-emption or grade-separation options. This could lead to extra costs caused by additional light rail vehicles needed to maintain the scheduled frequency16.

Accessibility, Land Use, Environment and Cost: Although giving the LRT a fully segregated ROW would eliminate the efficiency issue, it creates a physical barrier, decreases accessibility (especially for people with special needs such as mobility impaired and aging population), and usually causes major disruptions during construction stages. The City of Edmonton lists four critical criteria in evaluating a grade separation option: Accessibility, Network Operations, Urban Design & Social Environment, and Feasibility and Construction17. Cost is always a key concern when determining the proper solution for an intersection.

Can crossings be improved?

There are numerous potential solutions that can be explored to mitigate inefficiencies and risks of current LRT-crossing technologies. It is important to compare and analyze new and current technologies to achieve the best possible solution.

 

Enhanced Audible and Visual Warning System

Audible warning systems using Bluetooth technology and video camera detection can provide more effective warnings to pedestrians and cyclists at an LRT crossing in locations where crossing gates are not installed18. The video camera detection can be used to detect an LRT approaching, road vehicles, pedestrians accidents and near-misses to trigger the warning19. Speakers emit a warning notification to indicate that a train will be passing shortly. The warnings are verbal pre-recorded messages. Aside from the audible warnings, pedestrians will be able to receive push notifications on their cell phones advising to put away their devices as they approach a crossing. The push notification is based on the geolocation proximity of the passenger in regards to the crossing location20. The technology can be further developed to allow warning to be sent out when a train is arriving shortly for additional protection.
There are also visual warning systems available, such as embedded LED lights which light up alongside the LRT crossing at the intersection, mimicking a crossing gate while using a virtual light barrier instead21 of a physical one. This technology has been used in a few systems in the world. While not yet widely adopted, it could be a further improvement in achieving an “urban style design” by eliminating physical barriers.

The advanced audible and visual warning systems can add an extra layer of protection, hence reducing the potential system downtime caused by accidents. However, it must be understood that such technologies still may not optimize any traffic flow or LRT operation. In addition, Calibration, operation in inclement weather, or operation in 40 below temperatures and maintenance affect effectiveness and costs of these solutions.

 

Lightweight LRV

With lightweight LRV22, the lighter mass of the LRV allows for better acceleration and deceleration. The enhanced deceleration increases the capability of the LRV to stop in case of emergencies near at-grade crossings. A lighter LRV also decreases power consumption for acceleration, while the improved acceleration and deceleration performance allows for quicker clearance of an intersection. A major problem with LRT crossing gates is the long gate time. With faster acceleration and deceleration of LRVs, the gate time could be effectively reduced, resulting in less traffic wait time. A similar effect can be achieved at TSP intersections as a shorter LRT phase time is required. However, it should be noted that the reduction of the LRT crossing time based on such technology could be limited, since other factors such as LRT operations, safety concerns including coordination with surrounding vehicles, bikes and pedestrians, and passenger comfort may limit the maximum acceleration and deceleration rates. Pedestrians and cyclists may also need to be more aware of the surroundings at grade crossings, where an enhanced audible and visual warning system mentioned in the previous section could be helpful under these conditions.

 

Emerging automation technologies for rapid transit

If the origin-destination (OD) information of all vehicles on the network can be collected proactively and communicated among each other, the resulting optimization could be even more effective. This is where adding emerging automation technologies to TSP come into play.

Train automation technology has been proven in the railway industry for decades such as Communication Based Train Control (CBTC) or Europe Train Control System (ETCS Level 4). However, the challenge is the communication between train and road vehicles. Emerging automation technologies can include two main categories: Connected Vehicles23 and Autonomous Vehicles24. The connected vehicle technology consists of data communications between connected vehicles and LRVs. Having the ability for connected vehicles and LRVs to communicate allows for more efficient management of traffic flow because traffic signal controllers’ detection capabilities will not be limited to the immediate area around the intersection. This technology will be most effective when the majority of vehicles are connected. Some North American equipment suppliers have indicated that mass production of the vehicle-to-vehicle communication components can start approximately 2.5 to 3 years after certain regulations are established25. An LRT system also is a highly beneficial platform to pilot connected vehicle technologies due to the controlled environment of the LRVs.

Autonomous vehicles can also further improve the efficiency and operation of an LRT system when they are used in conjunction with connected vehicle technologies. The Society of Automotive Engineers (SAE) defines six levels of automation, classified from no automation (level 0) to full automation (level 5)26, and it is predicted that a mass deployment of fully autonomous (level 3-5) will be achieved in the 2030s or 2040s27. Any emergency situations that happen at level grade crossings can be communicated by the vehicles to the LRV through connected vehicle technology to allow for coordinated action between vehicles and improved safety. The technology could potentially enhance the TSP technology, and may even further eliminate the need for most signals and gates if fully implemented, reducing the cost of crossings.

It is important for transit agencies and governments to be aware of the predicted timelines for these technologies and prepare for their arrival. Although these technologies are still being developed and tested today, it is not advised that one should simply sit and wait for it to happen while the congestion continues to build up. Instead, infrastructure upgrades and other solutions for LRT crossings need to be planned and designed carefully in the mean time to prepare for a future of greater efficiency throughout its life-span.

On the other hand, considering that these technologies would reduce the need for major infrastructure upgrade or protection equipment (similar to the TSP solution), it is beneficial when considering an “urban style design”, as it does not divide communities. However, extra attention needs to be drawn to pedestrian/active mode user safety due to a lack of physical protection equipment.

A combination of various advanced technologies may further improve efficiency, such as applying an “advanced audible and visual warning system” to address safety concerns and using lightweight LRVs to reduce the LRT phase time. In all cases, it is essential and necessary to apply simulation tools to evaluate the overall performance of an intersection28. The figure below demonstrates an ideal scenario where advanced technologies can be applied to an LRT level crossing.

ENHANCED DESIGN FOR AN LRT LEVEL CROSSING WITH INTELLIGENT INFRASTRUCTURE

Transit-oriented land development

If grade separating an LRT crossing is inevitable, applying transit-oriented land development for the land that sits on top of a grade separation not only makes the area more visually appealing, but can also bring communities closer together. One example is the proposed “Rail Deck Park” over Toronto’s Union Station Railway Corridor29. In many cities around the world, elevated transit structures are integrated with new development such as major shopping centres, parks, trails and recreation areas. The Caulfield to Dandenong Open Space is another great example of such integrated re-development of a railway grade-separation project in Australia30. Metrolinx has proposed similar concepts such as “Mobility Hubs” in the new Regional Transportation Plan31, which integrates transit with land use in order to make such hubs ideal places for people to gather and relax. To further enhance passenger experiences, advanced technologies could be adopted, such as providing live transit arrival, departure, transfer, and delay information through cellphone and passenger information displays. Stores at these transit hubs could provide pickup services to passengers who place their orders ahead of time. Stations themselves can also be eco-friendly by applying advanced materials and smart building systems32. These measures can encourage people to use the transit facilities and make the grade-separated structure more sustainable to the community and environment in general. However, the initial investment cost for these transit hubs remains high.

 

How crossing technologies are evolving

The diagram below shows a summary of how current technologies (Intersection options categorised as “Today”, on the left) could evolve as future solutions to improve the overall design of intersections based on the research discussed in this paper. With the implementation of future advanced technologies, LRT crossings can evolve into more intelligent infrastructure (Intersection options categorised as “Future”, on the right), improving performance with fewer downsides for cost, safety, LRT operation, road traffic and pedestrian flow, and environment and land use.

Technology advancement for an LRT intersection

What are the next steps?

As technology evolves, emerging technologies can potentially address many of the problems that the current solutions are suffering from, while offering additional benefits. However, it is important to keep in mind that no technology is perfect. Each carries its own benefits as well as deficiencies. At the same time, there is not a simple one-for-all solution for each LRT crossing, and a comprehensive evaluation of each case is necessary. There are constantly evolving and technologies available such as enhanced audible and visual warning systems as well as advanced TSP systems; at the same time, it is also critical to see the trend of intelligent infrastructure and understand all the available technologies that can be offered as potential solutions to be Future Ready™.

To further develop our understanding of the topic, next steps are proposed as below:

  • Continue research on potential technologies in other disciplines where ideas can be borrowed and applied to further advance LRT level crossing technology
  • Undertake studies to identify types of intersections that have inefficient technologies and how they can benefit from better grade crossing solutions
  • Leverage WSP’s knowledge on intelligent infrastructure and work with local municipalities to increase the interest of designing and implementing better grade crossing solutions for their city
  • Collaborate with solution providers, municipalities, transit agencies for Research and Development activities on the potential solutions

Well-designed LRT systems can effectively move passengers and reduce traffic congestion. What if we can advance intersection design to allow all types of transportation users to cross in a safe and efficient manner?

 

Reviewers

Jennifer Verellen, P.Eng., IntPE
Mustafa Mirza, P.Eng., PMP
Yan He, Ph.D., P.Eng.
Chris Walsh, P.Eng.
Stephen Doubek, B.Sc.
Anna Robak, P.Eng., Ph.D.

Authors

Yishu Pu, M.Sc., EIT
Herman Won, P.Eng.
Henry Chiu, P.Eng.
Mark Del Biondi
Nathan Breeze, BES
Tianna Henry-Lewis, B.Sc.
Darren Dalisay
Thomas Lieou

 

References

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  11. Ibid.
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  13. Transforming Edmonton » Sustainable Urban Integration – Connecting Edmonton to its Routes.
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  19. 5 Use Cases of Video Analytics in Public Transportation -. (2017).
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  30. Caulfield to Dandenong Open Space | Your Level Crossing. Available at: https://your.levelcrossings.vic.gov.au/public-open-space. (Accessed: 29th October 2018)
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