[Velomobile] Problems with velomobiles

[Frederik Van De Walle]

Elrey is concerned with roll-over accidents with trikes and velomobiles, a very valid concern. Current velomobile experience does show that velomobiles are relatively very safe, but indeed that can change when in the hands of less experienced members of the public. 


Safety is always a concern for any designer with a conscience. I think about it almost daily. You can do your best to design the vehicle as safe as possible within the chosen general lay-out, one can warn for the possible dangers (personally, or in a manual), one can give driver training and/or restrict access (drivers license or 'sign here, stating you understand the risks of using this vehicle and have understood how to operate it'. ) and lastly, one can hope and pray that nothing bad happens because ultimately, you can't control the user.


Roll-over accidents happen with velomobiles, and more so if they become more widespread. As such a velomobile would need proper roll-over protection, a roll-over bar or even a structural roof. Preventing roll-over accidents completely is impossible, making the vehicle wider will move the treshold - but when it happens it will hurt just as much or even more given that it will happen at higher speeds. So as the likelyhood reduces, consequences become bigger. Yet the combined risk is surely lower for a wide vehicle.  Unfortunately, making a velomobile as wide that it will be less likely to roll than a car, will reduce many of its other wonderful properties and indeed compatibility with cycling tracks. I don't believe that a tilting trike is a solution either, as once you reach the vehicle limits, you too can skid and fall/roll or in worst case, flip over. We have a very real limitation here. Acting upon that, the manufacturer has an responsibility to make
 the vehicle safe as can be done. When talking 
open trikes, there is only so much one can do. If a velomobile body is 
structural, it will be easier but also more expected that one 
incorporates roll-over protection. 


But we also need to understand that the end user also has a responsibility. To operate any vehicle safely, the end user needs to understand that any vehicle has 
limitations, and that it is your responsibility to operate it within 
those limitations. The job of the manufacturer/reseller or just a simple user who lets somebody have a go, is to communicate what limitations 
exist if a new user is unfamiliar. When people test drive, I have always warned for that your typical velomobile will 
roll-over sooner and often demonstrated a 2-wheel turn 
(wheelie ...) to illustrate it. 

Comparing/illustrating again. Yes, it is tempting to think that cars don't roll. That, or we use them within their limitations. It was swedes that made the scandal with the Mercedes A-class that rolled over in their moose evasion test caught on film and widely spread. Indeed, it looked bad. But truth is, many cars will roll if only you yank that steering wheel hard enough in one and then quickly after the other direction. Yet almost everybody understands that this is not done. I also like to make the comparison to a sports motorbike that has very severe limitations to what a user can do. Anybody with a license (which older generation just got as an extra with the car licence) can buy then, but not everybody should be using them. Most people understand that, some don't. Because when observing objectively, simply 'using' the throttle can have disastrous consequences on the majority of motorbikes for sale. Yes, the latest and most expensive iterations have
 traction control - but a few touring bikes apart, the prime function to go faster, not prevent noobs from user error. A similar thing applies for the brakes. Now ABS is more common, but before squeezing the front brake meant you opted to continue your travel by air, willing or not. I a similar fashion, the same can be said with bicycles when the first V-brakes and disk brakes came. 


So we need to be sure that people approach a velomobile with respect, and not as a fail safe toy. We all have a responsibility there and it is good to be aware of this. That, and that you need to spell out to new users what is obvious to regular users. 

Concerning blow-outs. Indeed, the windcheetah is very twitchy without rear grip. Good fun, but with a blow-out, very hard to control. And indeed, a single rear wheel and a blow-out are not a nice combination. At the same time, one needs to remember that few vehicles are safe in such a situation. Any vehicle with a rear tyre blow-out is prone to oversteering if doing anything more than travelling in a straight line. Oversteer and rolling over go together. Nowadays cars have stabilisation systems like ESP etc. (since nov 1 2011 required by law for new cars to get a european type approval) and some have run-flat tyres that do much to keep a car safe during a blow-out. This is definitely a big step forward. Perhaps some kind of run-flat system for the rear tyre is something to consider for future velomobile tadpoles, too. In the end though, one still relies that one doesn't blow out close to it's maximum dynamic capabilities. And as far as statistics go, if
 I recall correctly, the most dangerous dynamic scenario for a single car has always been oversteer for whatever cause and - with speed involved, the high risk of ensuing roll-over(s). That is why just about every car for sale has a chassis set-up for understeer. The same applies for velomobiles. Contrary to what might assume, the tadpole in not necessarily more prone to understeer because of the single rear wheel, it really depends on many things in the design. Apart from blow-outs, delta trikes actually have a greater tendency to oversteer because as the inner wheel lifts, the slip angle increases more in the rear than the lighter loaded front tyre. 

Safety is a strange thing. From the above one would assume this velomobile would be the safest: http://www.ecofriend.com/entry/the-world-s-slowest-porsche-911-is-pedal-powered/. Yet you will easily finds people who shall disagree. And we haven't even started talking about risk compensation effects of any safety measure. 

So perhaps the most important thing is to communicate properly at all times and to adjust one's behaviour to the perceived safety of the vehicle at hand. It is better to underestimate than to overestimate how safe a vehicle is. And it's user. All too many have a tendency to overestimate. Remember that.

Cheers,
Frederik