Speed Does Matter

Time is a critical factor in the design of a car user interface. When using the car systems, drivers have to divide their attention between following traffic, controlling the vehicle, and using in-car equipment. Traffic psychology specialists have extensively studied the drivers’ divided attention and its impact on driving performance. They have shown that the control of a car is affected by both how long the driver’s eyes are away from the road and the total time of the secondary task, specifically, the operation of an in-car device.

There are big differences between individuals. Experienced drivers can control their cars using their peripheral vision much better than novice drivers can. On the other hand, it is impossible even for them to react quickly in emergencies if their eyes are directed away from the road. A general rule of 4 x 1.5 (preferably 3 x 1.2) seconds for the maximum duration of a secondary task has been suggested.[1] According to this rule, any task performed during driving must not require drivers to take their eyes off the road more than 4 times longer than 1.5 seconds at a time. The following figures give an idea about the distractive effects of some common tasks drivers carry out:[2]

ACTION

NUMBER OF GLANCES

LENGTH OF GLANCE, SECONDS

Reading a speedometer

1.26

0.62

Inserting a cassette

2.06

0.80

Manually adjusting a radio

6.91

1.10

These figures gave us a framework for designing and evaluating solutions for in-car secondary tasks such as finding entries in a contact directory, adjusting receiver volume, and browsing a calendar.

In terms of the Steering Wheel project’s methods, the importance of the user’s divided attention meant that UI solutions had to be evaluated right from the start in a dual-task environment. The primary task had to approximate driving with respect to its attention-catching requirements, and the test environment had to physically resemble the dashboard of a car so that the control elements could be placed in their “natural” places within the drivers’ physical reach and line of sight.

How to test was initially a problem for the project. A real car couldn’t be modified enough to meet the needs of each different test situation. And tests with unfinished prototypes would have been downright dangerous—not a defensible risk for a project intended to design safe traffic products. Car factories and research facilities have expensive and advanced simulation environments that can move the car’s chassis dynamically so that the driver gets a natural sense of acceleration when speed fluctuates and during turns. This kind of simulated driving environment can be fine-tuned so that the driving experience closely resembles the reality. (In the best simulators the environment is projected onto a hemispherical shape that covers the driver’s entire field of vision.) Hiring a test environment would have been an option if we had testproof prototypes ready for a compact evaluation session, but we didn’t. We needed a simulation environment at our disposal throughout the project for small-scale experiments and iterations of the most interesting ideas. The simulation environment phase of Steering Wheel was budgeted for about one calendar month and had a limited amount of funding with which to create a simulation environment, so anything fancy was out of question.

[1]H. T. Zwahlen, C. C. Adams, and D. P. DeBald, “Safety Aspects of CRT Touch Panel Controls on Automobiles,” in Second International Conference on Vision in Vehicles, A. G. Gale, M. H. Freeman, C. M. Haslegrave, P. Smith, and S. P. Taylor, eds. Nottingham, U.K., Sept. 14–17, 1987. Amsterdam: North-Holland, 1988, pp. 335–344.

[2]M. Mollenhauer, M. Hulse, T. Dingus, S. Jahns, and C. Charney, “Design Aids and Human Factors Guidelines for ATIS Displays,” Ergonomics and Safety of Intelligent Driver Interfaces, Y. Noy, ed. Mahwah, N.J.: Lawrence Erlbaum, 1997, pp. 23–61.



Mobile Usability(c) How Nokia Changed the Face of the Mobile Phone
Mobile Usability: How Nokia Changed the Face of the Mobile Phone
ISBN: 0071385142
EAN: 2147483647
Year: 2005
Pages: 142

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