The standard was developed with input from transit operating/planning agencies, manufacturers, consultants, engineers and general interest groups. Designing and integrating HMI control systems is a task often undertaken by specialized suppliers to complement the core capabilities of end product manufacturers, in this instance, rail car manufacturers. Some manufacturers use an HMI supplier as an extension of their design team, a knowledgeable partner who provides added design capacity and fast turnaround.
The task of an HMI System is to make the function of a technology self-evident to the user. In passenger access applications, the HMI has to be intuitive, easy to see and understand, and clear in its feedback to the passenger.
Trends in HMI Systems for Passenger Access
Trends in HMI Systems for passenger access include better illuminated symbols and indicators, the addition of simple and complex tones to provide audible feedback, sealed HMI components, and "hidden-until-illuminated" controls.
In addition, programmable doors are becoming more popular. Here, the amount of time for the door to close, the amount of force acting on the door, and the amount of force necessary for emergency or manual release are adjustable through a programming interface within the door control system.
HMI Systems that offer reliable, intuitive and ergonomic performance are essential to both the passenger and rail crew. In the United States, the ADA regulations require that controls be accessible for passengers with disabilities, utilizing the overall simple functionality and ease-of-use criteria applicable to public access applications.
Passenger Audible Alerts
The main function of audible alerts is to notify passengers of door motion, either opening or closing, or to alert the instance prior to these actions. This is the main reason for multitone sound devices. There is great benefit with multitone sound units for door system installations that generate alert tones locally at each doorway, as opposed to generation of sound via the passenger communication system.
Passenger applications often use audible feedback, such as voice/sound indicators. Passenger HMI controls can also include override systems, and emergency-call equipment prompted by audible, visual, and hidden indicators, and programmable acoustic warning signals. In addition, the audible alert is sometimes used to help visually impaired passengers locate door actuation pushbuttons or the doorway opening. A unique tone is emitted that maintains a sound level in the approximate range of 2 to 5 dB above the ambient sound level. This allows the tone to standout from the noise commonly found in the environment.
In Europe, the European Technical Specification for Interoperability for Persons with Reduced Mobility (TSI-PRM) makes it easier for disabled passenger to use trains by setting standards for passenger access and on-board information. It applies to all heavy rail (train) vehicles on the major lines of the mainline rail system in Europe.
TSI-PRM sets standards for audible sound pressure levels of door opening alarms, the intensity of lighting within a car and at the station, height of door access controls, even the amount of force required to activate a switch. In addition to setting the requirements for door controls, it also stipulates standards for on-board toilet facilities, including controls which allow access to the restroom, door locking, toilet flushing, and washing, all must be compliant.
Functions that must be considered under TSI-PRM in upgrades include:
- Seats, back grab handles on seats;Wheelchair spaces;
- Exterior and interior doors;
- Information displays;
- Height changes for controls, etc.;
Standard HMI components for passenger use could include:
- LED illuminated pushbutton switches and indicators;Emergency stops;
- Keylocks, levers, and rotary switches;
- Emergency passenger alert functions;
- Switch systems that incorporate all the necessary information required for a passenger, including pushbutton, indicator, and feedback with visible and audible notification and easy location with an ambient responsive finding signal;
- Keypads and keyboards;
- Programmable audible alerts;
- Responsive audible alerts.
Controls must also be durable and as "mistake-proof" as possible. In addition, control systems need to interface with other onboard equipment. Choosing the right communication interfaces is a key part of the design of the HMI System, whether that includes hardwiring, bus systems, or even wireless communications.