HMI Systems for rail consider passenger use from every angle. In addition to meeting regulations for ADA and Rail Vehicle Accessibility, HMI Systems also consider everything from environmental demands to aesthetic appeal.
To address potential environmental concerns, stainless steel and durable polymer-based products are often given top consideration for reliable operation under demanding conditions. Where required, control products fabricated from these materials offer protection up to IP 67, as well as resistance to heat, shock, vibration, and vandalism. They are designed for minimal maintenance and long-term use and abuse. They deliver a long lifecycle at a great cost-benefit – very appealing to transportation companies.
The International/Ingress Protection, or IP rating system, is widely used throughout Europe and describes the degree of protection as defined by the International Electrical Commission (IEC) standard 60529. The degree of protection as defined by the IEC is used to describe:
Protection offered to people against hazardous parts inside and enclosure;Protection of equipment inside the enclosure against the intrusion of solids;Protection of equipment inside the enclosure against the ingress of liquids.
HMI devices are defined as an enclosure by the IEC. The rating proves the device has been tested according to international standards, providing a more detailed measure than arbitrary terms like "waterproof."
In an IP number, for example IP 67, the first number is a measure of how well the enclosure can prevent an invasion by solids – 6 is dust tight. The second number represents the measurement of protection against liquids at various pressures – 7 indicates protection against immersion beyond one meter. Most passenger rail applications demand a minimum IP 67 for external HMI components, due to the risk of immersion.
Illuminated pushbuttons are often found in passenger rail door applications. Featuring a bright front bezel, LED halo illumination, and a large touch surface that can be supplied with Braille text for the partially sighted, the illumination immediately focuses user attention on the control. These pushbuttons are also immune to the harshest graffiti cleaners available.
In safety and security applications, crew key switches protect against unauthorized access and act as additional safety controls.
Each switch actuator is comprised of a unique rotor shape identified by the transit authority. These special purpose keylock switches are ideal for heavy, commuter, and light rail environments and can be used in flush-mount designs for increased vandalism resistance.
In addition to passenger door control, HMIS for doors in on-board public restrooms must be reliable, visible, and easily operated. Wheelchair access requires that pushbuttons are fitted to certain heights and operable by palm. In passenger toilet compartments, there are several functions that must be easily defined and accessible, in addition to toilet control. These include multiple passenger emergency positions for signaling an emergency to the crew, door lock/door open, lavatory controls for water, soap dispenser, hand dryer, and others.
Balancing aesthetic appeal and standards
Aesthetic considerations are a powerful factor, since these systems are often the primary interface between the transit entity and the rail public. Controls that combine aesthetically pleasing design with ease-of-use create a good impression and actually make operation more foolproof for the passenger.
In rail, great HMI design begins with understanding the user. Often, there may be a defined standard that captures the user's best interests and highlights best practices. These include federal human engineering standards, such as those set by the ADA, the American Public Transportation Association (APTA), the Department of Transportation Federal Railroad Administration, the International Railway Industry Standard (IRIS); and HMI guidelines from industry organizations, such as the American National Standards Institute (ANSI), IEEE, ISO, and others.