Are outward sliding door systems the new standard?

With Australia’s bus fleets evolving rapidly towards electrification, every aspect of vehicle design is coming under new scrutiny. One of the most overlooked yet functionally critical decisions is whether to choose inward-gliding or outward-sliding door systems. This is not just a matter of aesthetics or tradition; it affects safety, passenger experience and total cost of ownership.

So, with electric buses shaping the future of public transport, the question must be asked: is it time to make the outward sliding door the new standard? We asked door systems specialist Ventura for the insights vehicle manufacturers and operators need to make the right decision.

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Swinging, sliding or gliding?

To be clear: is a swinging door the same as a sliding or gliding door?

“Let’s begin by clarifying the evolution of door systems,” Ventura Systems Australia general manager Wolter Meijerhof, explains to ABC.

“Traditionally, buses used inward gliding or outward swinging doors (literally swinging outwards). However, with the introduction of Ventura’s outward sliding plug door, which moves outwards before sliding closely alongside the vehicle body, outward swinging doors have largely been phased out.

“One of the main drawbacks of outward swinging doors was their wide arc, which posed safety risks and increased the risk of entrapment. The technology was also relatively basic, with large components visible and taking up interior space. While still common in coaches, they are rarely used on high-frequency urban buses in Australia.

Example of a bus with outward swinging door systems. Image: Ventura Systems Australia

“Today, in Australia and New Zealand, the industry standard has become either inward gliding or outward plug sliding doors. The double inward gliding door remains the most common choice for vehicle manufacturers and operators. As fleets modernise, especially with the move to electric and low-floor vehicles, outward plug sliding doors are increasingly preferred, particularly in Europe, due to their operational benefits. We expect this trend to grow locally as well.

“Ventura offers both double-leaf and single-leaf outward plug sliding doors. The single-leaf version can be used as an entrance door or an additional door at the rear of the vehicle. Both the double-leaf and single-leaf doors fit within the same portal dimensions as traditional inward gliding doors.”

A clear example of this shift can be seen in the Brisbane Metro Bus Rapid Transit (BRT) system, introduced by Brisbane City Council. The HESS lighTram25, a 24.5-metre, bi-articulated electric vehicle with a capacity of up to 170 passengers, features three wide outward sliding double doors designed to optimise passenger flow during boarding and alighting.

At the front, a specially developed rapid outward sliding door provides a dedicated entrance to the driver’s compartment. By moving outward rather than inward, this system not only preserves valuable interior space but also delivers superior sealing performance, enhancing climate control and reducing noise ingress.

Out or in?

Does it really matter whether a door opens inward or outward? Isn’t a door just a door?

“It definitely makes a difference. Take rail transport, for example. Trains have used outward opening doors for a long time because they run on flat, straight platforms with enough clearance. Buses, on the other hand, especially in tight urban areas, have historically avoided outward opening doors. This is mainly because of the risk of hitting nearby obstacles,” Meijerhof says.

“That changed with the introduction of plug sliding doors. These doors open outwards and then slide along the side of the vehicle, thereby eliminating the risk of hitting kerbs or street furniture. Thanks to the plug technology, the distance the door opens outwards is minimal and the door leaves won’t strike the curb. Interference with wheels or mirrors is also not a concern, as the door leaf can be precisely angled to move away from these components during operation. As a result, they’re perfectly suited for narrow urban streets.

“But there’s another important reason trains use outward opening doors. They offer superior sealing because they close over the exterior of the portal, rather than pushing outward from the inside. This is especially important at higher speeds where it makes a noticeable difference. Better sealing means less road noise, which improves comfort for both drivers and passengers. It also helps to keep water, dust, and dirt outside the vehicle, contributing to a cleaner and quieter cabin environment.

“Outward opening doors also offer significant advantages in terms of interior space. By eliminating the need for inward door movement, the area behind the doors, which is currently designated as a no-standing zone under Australian guidelines, can be utilised by vehicle designers for standing passengers, additional seating, or to improve accessibility for people with disabilities. Additionally, when deploying a ramp for mobility-impaired passengers, outward opening doors provide more room to manoeuvre, making boarding and alighting easier and safer.

“Outward opening doors significantly reduce dwell time by allowing all-door boarding and alighting. Unlike current designs with no-standing zones, they create an unobstructed passage, improving passenger flow and enabling quicker stops.”

Table showing scoring on aspects of specific door systems. (+ is positive impact).

Modern entrance solutions

An outward sliding door sounds more complex at first glance. So, why should vehicle manufacturers or operators opt for this solution?

“Compared to traditional inward gliding doors, outward opening doors may involve a higher initial investment, but they offer significant long-term advantages in terms of total cost of ownership, passenger flow and safety. Since introducing the Plug Sliding door, we have continuously refined its design, drawing on over 30 years of global field experience to further enhance its performance and reliability in daily urban operation,” Meijerhof says.

“A common challenge with inward gliding doors is managing the floor slope at the entrances. The door’s sealing must be flexible enough to tightly seal the doorway when closed, yet also accommodate the slope as the door moves inward. Many competitors rely on rubber seals or brushes to handle this clearance, which compromises sealing effectiveness, resulting in increased noise and allowing more water and dirt to enter. Additionally, these components require frequent replacement adding to more cost.”

To address this, Ventura Systems has engineered a durable, active flap mechanism for their inward gliding doors that securely seals the doorway when closed and opens to clear the slope during door movement. This innovative solution improves sealing performance and reduces maintenance needs.

“Finally, our outward sliding door improves safety for passengers. The design of the door provides better safety due to its over centre locking system. Because the door leaves lock over the centre of the pivot, all the weight of the door leaves is pushed towards the inside of the vehicle,” Meijerhof says.

“This means that when the doors are closed, it is impossible to open the door leaves manually. In an emergency the passengers can use the emergency button or manual emergency lever to safely exit the vehicle.”

Future developments

Locally we see a lot of double door leaf doors being used. Is there a market for the single leaf outward opening door?

“In Australia and New Zealand, single-leaf outward opening doors are occasionally used as rear exit doors, and sometimes as both front and rear doors on minibuses. This trend is also growing across the Asia-Pacific region, where smaller vehicles benefit from the single-leaf door’s ability to maximise interior space while providing a reliable and safe entry solution,” Meijerhof says.

“The single-leaf door is also commonly used as an additional rear exit, as seen in Singapore, where a rear staircase requires a more compact door solution. Our Rapid Sliding Door is ideal for this setup and can be adapted into a wider front door as well, offering flexible solutions for diverse vehicle layouts.”

“In summary, it is worth taking the time to carefully evaluate the configuration of the door system that is best suited to the application. As fleets transition to electric and more modern designs, it’s a good time to re-evaluate long-standing choices and consider more future-ready solutions. We are fully committed to supporting vehicle manufacturers and operators in making the right decisions.”

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