Those who ignore history


BMW HUD concept (Image source: BMW) Those who cannot remember the past of human factors are doomed to repeat it…

With apologies to the philosopher George Santayana, I’ll make the point that the BMW Head Up Display technology is in fact not the unalloyed blessing premised by BMW in their marketing material.

The downside, which the BMW engineers seem to have overlooked or not understood, is that HUDs are notorious for an effect called cognitive tunnelling. That is where a person involuntarily, and undesirably, fixes their mental resources on an information source, for some length of time, at the expense of monitoring other critical elements of the environment.

You are driving at 100 km/h on the motorway and glance at the speedo. Just one brief moment – yet you’ve just missed 28 metres of your route. That’s 28 metres in which a lot can happen. Unless, that is, you could pay attention to everything at the same time: such as with the BMW Head-Up Display….All the information individually selected by the driver with the BMW Head-Up Display activated appears there exclusively and no longer on the instrument panel. All in full colour and in brilliant resolution.

BMW online marketing material – retrieved 29 April 2013

Unfortunately, for the BMW engineers, putting information in the field of view leads to attention being focused on a much smaller Usable Field of View (UFoV), approximately 1 to 2% of the overall FoV. This leads in turn to the cognitive tunneling effect mentioned above. Nor is this a ‘theoretical’ effect, as studies of real world driving tasks have demonstrated (Lee and Triggs 1976; in Bossi, Ward, Parkes and Howarth 1997).

From a safety perspective this means that when HUD data is presented in the field of view there’s much less spare driver processing capacity left over to monitor the environment for high criticality low probability events. Such as, for example, a pedestrian stepping out into the street from between a pair of parked cars.

While certain performance advantages may be expected, drivers’ responses to some safety-critical events may be slowed significantly.

NHTSA Interim Report HS 808 320, 1997

Nor can we assume (unlike the aviation industry) a degree of homogeneity in the user population. The driving population covers a wide range of ages, and unfortunately we also know that the older one gets the poorer one’s UFOV becomes, which in turn ensures much greater cognitive channelling. This is one of the major reasons why there’s a higher rate of intersection accidents amongst older drivers (Ball and Owsley 1991). Now what was the demographic for BMW owners again?

Research has also consistently found that attention narrows under conditions of high arousal (e.g., high workload and/or stressful environments). So when driving at night, in bad weather or in an unfamiliar city a drivers ability to monitor for external events is going to be at an all time low, probably not a scenario where you’d like to further channel already limited attention into HUD data. Of course this is something of a problem for the HUD designers because what they’re trying to achieve is to ease the driving task, under these conditions…

Add to this the ability of the user to add information to the display, e.g ad hoc re-engineering of the interface, and the use of colour coding which can have unforeseen interactions with a dynamic background and you have, in my opinion at least, a complex error trap for drivers. And we’re going to throw this challenge at the older driver cohort who also have the recognised poorest performance in this regard?

As to how BMW were able to do what they did? I’d compare the relative immaturity of the automotive industry, in it’s regulation on system safety and human factors, to that of commercial aviation where there exists in contrast a strong national regulator with a culture of addressing the human machine interface issues of emerging technologies, all within a formal system safety management framework.

No BMW, as it turns out you can’t pay attention to everything at the same time, and designing an interface on that basis is asking for trouble.

Postscript – 2 Sept 2103

I’ve added an additional reference to a 2013 study by Cheng et al on HUD design. They found that the optimal display for driver speed stability was actually a low transparency HUD with an outline speed limit and a white and round speedometer.But they also found that the optimal combination for response time is high background transparency, outline speed limit symbol, green and a level (flat line style analog gauge) speedometer. found the users had bad performance to operation the speed and had longer response time for solid road speed limit symbol, orange and round & digital speedometer on HUD.


Ball, K. and Owsley, C. (1993). The useful field of view test: A new technique for evaluating age-related declines in visual function. Journal of the American Optometric Association, 64 (1).

Bossi, L. L., Ward, N. J., Parkes, A.M., and Howarth, P. A. (1997). The effect of vision enhancement systems on driver peripheral visual performance. In Y.I Noy (Ed.). Ergonomics and Safety on Intelligent Driver Interfaces. (pp. 239-260). Mahwah, NJ: Lawrence Erlbaum.

Cheng-Hung , H.,Chun-Wen, C., Tienwei, T., Ming-Hui, H. The Effects of Interface Design for Head-Up Display on Driver Behaviour. Life Science Journal 2013; 10(2): 2058-2065, 2013.

The Scientex Corporation – Human Factors Division, (1997) Human Factors Aspects of Using Head UP Display in Automobiles: A Review of the Literature, DOT NHTSA Report DOT HS 808 320, NTIS, 1997.

5 responses to Those who ignore history


    I’m a physician and supervise medical residents working with non-surgical patients in an academic hospital. We have a program of simulation for training and practicing response to cardio-pulmonary arrests (the resident trainee practices the team leader role and the others responding practice quickly coming together and functioning as a team). The responding (leading) residents have studied the algorithms and know the material well. Some manage the simulations fairly well, some make clear errors, generally due to missing key information (failure to elicit or misinterpretation/faulty sensemaking), but occasionally some will be paralyzed; kind a freeze or a deer-in-the-headlights phenomena. Sometimes there’s a loss of situational awareness due to over-focus on one thing; ie difficult airway, and I think this is similar to what you are describing as cognitive tunneling, but sometimes something else is clearly happening; the resident seems to have become cognitively (and almost physically) paralyzed. We address this, successfully in most cases over time, with repeated practice and check list prompts. I believe this cognitive paralysis (of some very bright people) is an electrochemical brain response, the fight or flight response that might more accurately be called the fight/flight/freeze response. From your engineering perspective, do you have any thoughts on this phenomena?


      Matthew Squair 04/05/2013 at 3:37 pm

      Hi Rich,

      Yes, it does sound very much like what some have called the paralysis response, especially the physical part. You see it often in crisis situations where people will appear to freeze and fail to respond to the crisis, for example in the Tenerife air accident many passengers who had survived the impact were found after the subsequent fire still in their seats with the seat belts still on. If you debrief your residents afterwards and they report feelings of dissociation and mental/physical paralysis then it’s a fairly good bet that that’s what’s happening.

      Although this effect is most documented in disasters it also occurs in other circumstances such as the example you gave. Nassim Talib the risk expert gave the anecdotal example of watching stock traders freezing while they’re losing all their portfolio. So a responsibility for decision making in a high consequence environment, which contains unexpected and/or unfamiliar challenges, also seems to be able to trigger this response.

      The likelihood of the effect occurring does seem to be correlated with the degree of stress response, animal experiments have shown that the more adrenaline in the body the more likely that a freeze response will eventuate, conversely rats with damaged amygdala don’t demonstrate a freeze response. In the case of your leading residents the stress related to fear of losing a patient, even a simulated one would probably be enough. There seems to be a feedback loop that occurs with the amygdala, with cortisol and other stress hormones feeding back to the amygdala which generates more stress hormones leading to the ‘deer in the headlights’ syndrome, unless there’s an intervention. In aviation and the military ‘freezing’ in training situations is also quite common, as I can personally attest to.

      The good news is that you can shock a person out of this state, a loud noise or yelling at them can do it (members of a team should be trained to monitor and intervene). Individual training in how to manage stress responses (e.g. breathing techniques) also helps by keeping adrenaline levels down and reducing the likelihood of a freeze occurring. Repetitive training through such stressor simulations definitely helps as it breeds familiarity (expertise) and agin drops stress levels, as you’ve found.

      One of the stress triggers can simply be information overload or task saturation, novices tend to be vulnerable to this as they don’t know what to attend to so they have to attend and think about everything. Experts on the other hand develop strong attentional management skills so they can economically manage their limited attention and cognitive budget. They also tend to be able to maintain an internal model of the situation better, are able to look for patterns and also predict where the situation is headed. All of which reduces cognitive workload, stress levels and the likelihood of a freeze event. Mica Endsley (on situational awareness) and Gary Klein (expert/naturalistic decision making) have done a lot of work in this area.

      The freeze response is a fascinating cognitive response, still a little mysterious as there hasn’t been a huge amount of study of it in humans. Gordon G. Gallup and John P. Forsyth have worked on the animal version, otherwise there’s a lot of anecdotal material from various accident and disaster reports. The best bet at the moment is that it’s a evolutionary survival strategy.

      I hope the above helps,


      Matt S.

      P.S. I also talked about the effect of stress on trained professionals here



    Surely it’s better to have information overlaid on the outside view than the inside? Otherwise, why would aircraft have had them for so long (and pilots do love them)?

    Information-overload is a good point, though; all you need are speed and simple navigation symbols at most, not that mess in your picture.

    Big fan of HUDs, btw.


      Matthew Squair 02/06/2013 at 9:39 pm

      There’s always a cost or trade off in these things. Yes pilot’s (especially military) love HUDs, but they’re also heavily selected and trained for an ability to maintain situational awareness, and HUD design has evolved through a pitiless evaluation process.

      The clincher for me is in the poor design of the HMI, all that alphanumeric information looks good, but it’s the most intensive to process and therefore sucks up most attentional resources. Then letting the end user modify the interface? That goes from ‘poor’ design to ‘no design’. So, my educated guess is that this is marketeering rather than engineering…



        Fair comments (apart from the grocer’s apostrophe 🙂 ).

        Being an ex-military (fast-jet) pilot, it’s difficult to know if my S.A. is better than the norm, or not. Perhaps it is, hence my like of HUDs?

        Either way, I think that we would both like something much simpler, clearer and less distracting. That probably makes the earlier car HUDs better than more modern ones.

        Can’t quite justify an M5 just to get one, though!