Road Network Operations
& Intelligent Transport Systems
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HMI Technologies

Humans can interact with the outside world, including ITS, in myriad ways and there is a wide variety of technology available to assist this interaction. The most common HMI components used are described here. HMI elements – good, poor and indifferent – are invariably present in computer systems and ITS. For example:

  • desktop computer-use – by persons at home in advance of their journey or in control rooms
  • personal mobile devices such as tablets and smartphones
  • public access personal interaction stations

Public displays may also incorporate important HMI features – such as:

  • public announcements that use an electronically stored or generated voice – or are automatically preceded by an “Earcon” (recognisable sound denoting, for example, information)
  • public visual displays (traffic and pedestrian lights, variable signage)
  • variable message signs

It is a commonly-held ‘truth’ that people have five basic senses:

  • vision
  • hearing
  • smell
  • touch
  • taste

In fact people have others senses as well, including: vestibular (balance and movement), kinaesthetic (relative position of parts of the body), pain, a sense of temperature and a sense of time passing. All these allow people to interpret the world around them, at different levels.

There is a wide range of human machine interface components to support the interaction between road users and ITS.

Engagement with ITS – HMI components

Use of hardware (such as buttons and a display screen) allow road users to interact and to develop a dialogue with the ITS technology. The extent to which the dialogue is efficient and effective (and liked by the user) depends both on the detailed design and performance of the interface hardware and also the design structure of the dialogue.

The designer of the HMI has a very wide range of choices. For example, in hardware design, buttons can be “latching” (they maintain their state after being activated) or “non-latching” (momentary) with different sizes, shapes and clearances to other buttons, different levels of resistance and sensitivity. The hardware design may also take account of implicit associations and knowledge of users (such as a familiar shape or icon and colour – such as red for danger).

The design of the dialogue (its structure and management) is also very important to promote ease of use. Important issues include: length of “timeouts”, language used and menu structure.

Although the design of the HMI of vehicles is the domain of the automotive manufacturer, in-vehicle HMI is often supplemented by drivers with the addition of mobile communications and information systems. These may or may not be designed for use while driving and their use can have a significant effect on drivers.

Advice to Practitioners

Choice of HMI is a specialist area, and advice from human factors professionals is recommended. The HMI should be based on:

There may be a trade-off between ease of learning and ease of use.

Try it with new users – what is their experience? (See Piloting, Feedback and Monitoring)

Human Factors and Road Signage

To be effective, all transport signs need to be noticed, understood and followed. Much has been studied and written about the human factors of road signage. Signage should be considered as part of an overall information provision strategy for road users. There will also be human factors considerations in its construction, installation and maintenance.

Variable Message Signs (VMS) are a typical form of ITS, particularly used on interurban roads to convey messages to drivers. Key considerations for VMS include:

  • VMS should possess appropriate features (such as colour, brightness, size, flashing lights or other indicators) which will distinguish them from non-variable signs
  • the legibility distance must allow drivers adequate time to read the sign “twice” whilst attending to their driving task
  • drivers should be able to finish reading the sign before their eyes are diverted more than 10 degrees from the road ahead
  • messages should be short and unambiguous
  • where possible VMS should use pictograms
  • the number of words (or information units) in one text message should be limited to seven

Vehicle and Driver-Related

Design of vehicles including their HMI is the domain of vehicle manufacturers who consider the “look and feel” of their vehicle’s HMI as part of their brand image.

Information and communication systems may be factory-fitted, fitted as an aftermarket option or (more commonly) brought into the vehicle by the driver. Examples include SatNav guidance systems and fee collection transponders. Some countries have legislation restricting the use of specific devices such as hand-held mobile phones. The HMI of in-vehicle devices may or may not be suitable for use while driving and road operators should be aware that use of such “secondary” interfaces by drivers may contribute to inattention and distraction.

Engaging Users through ITS in Data Collection

Some Road Operators and other information brokers have sought to use data provided by large numbers of transport users to help road performance. This is called “crowdsourcing” which uses location and communication information from smart devices. The engagement of users may be implicit as a result of their use of other services, or may require more explicit participation. Increased engagement and richer data may be sought by offering interaction and competition (“gamification” – turning it into a game) or by using user-derived content from social media. There are privacy issues to consider, but road users may be willing to engage in services that offer benefits to them, such as ride sharing.


Reference sources

Dewar, R. and Olson, P. (2002) Human Factors in Traffic Safety. Lawyers & Judges Publishing Company, Inc. ISBN 0-913875-47-3

Sanders, M. and McCormick, E. (1993) Human Factors in Engineering and Design. McGraw-Hill, Inc. ISBN 0-07-054901-X

British Standards Institute (2002) BS EN ISO 15005:2002 Road vehicles – Ergonomic aspects of transport information and control systems – Dialogue management principles and compliance procedures

Castro, C. and Horberry, H. (2004) The human factors of transport signs. CRC Press Boca Raton ISBN 0-415-31086-5

Mizar Automation (1991) White Book for Variable Message Signs Application. VAMOS DRIVE project deliverable. October 1991.