Getting Mobile on Two Wheels
Whether motorized or not, there can be no doubt that traveling on two wheels is “in” right now. This is due in no small part to the exponential increase in the variety of different bikes and high-tech equipment available, as well as the political trend towards promoting cycling as a mode of transport – especially in towns and cities – in order to help protect the environment. However, getting mobile on two wheels always comes with a higher risk of suffering a severe accident than traveling by car, van, or truck. As road users with little to no protection, riders of two-wheeled vehicles are usually the ones who come off worst in case of a collision.
For years, around 25 percent of all those who have died in road traffic accidents worldwide have been users of motorized and non-motorized twowheeled vehicles. The figures for the EU are similar: in Germany, for example, around a third of all road users killed in 2019 lost their lives after suffering an accident while riding a bicycle or motorbike. By way of comparison, figures from 2017 – the latest data available – show that users of two-wheeled vehicles accounted for around 16 percent of all the people who lost their lives on the road in the USA. For decades, however, accident rates have been highest in heavily populated developing and newly industrialized countries, where mass mobility on two-wheeled vehicles is a prominent feature of the society.
So how much greater is your risk of dying in a road accident in Germany, for example, if you ride a motorcycle instead of driving a car? We can assess this by comparing the number of deaths to the number of registrations for the vehicle type in question. The number of deaths among motorcyclists was 605; around 4.5 million motorcycles were registered. The number of deaths among car drivers and passengers was 1,364; around 47.7 million cars were registered. This means that, for every 100,000 vehicles registered, 13 motorcyclists and three car drivers/passengers lost their lives. This disparity becomes even more stark when we take into account the fact that motorcycles have a far lower mileage. The EU Commission was already saying years ago that the chance of being killed on the road was around 18 times higher per kilometer covered for motorcyclists than for those traveling by car. Incidentally, the EU Commission calculated this risk as being seven times higher for cyclists.
These few figures alone show that there is still a drastic need for action when it comes to road safety for users of two-wheeled vehicles, particularly as mobility on two wheels is likely to increase even further in the next few years. This applies to both motorcyclists – be they leisure bikers or commuters – and, in particular, to cyclists and users of electrically assisted bikes. According to data published by the ZIV, an association for the bicycle industry in Germany, bicycles and e-bikes are the perfect modes of transport for short and medium-distance journeys. The ZIV also states that, according to the results of several studies, freight bicycles could account for around 50 percent of all motorized goods transport in cities in the future. However, the more cyclists there are on the roads, the harder it will be to find a suitable way of apportioning the available road space – a division that still heavily favors cars in many areas of the world. Another source of potential conflict is also emerging alongside this familiar “battleground”: the increase in micro-mobility, which is the term used to refer to people using personal light electric vehicles such as e-scooters and self-balancing vehicles such as Segways to get around.
The fact is, as road users with no cabin to protect them, riders of two-wheeled vehicles are always in danger of suffering severe or even fatal injury if they become involved in a single-vehicle accident or a collision with another vehicle. The following chapters of this report will go into detail on what action can be taken to significantly reduce this risk for the various vehicle categories, from e-scooters, bicycles, and pedelecs to small mopeds, mopeds, and motorcycles.
THE LIMITS SET BY DRIVING DYNAMICS
In this context, it seems sensible to take a moment to familiarize ourselves with a few of the physical peculiarities of two-wheeled vehicles as a mode of transport. For example, why do motorcycles and bicycles not fall over when traveling in a straight line? After all, they are subject to the laws of gravity, just like everything else in the world. Some motorcycles weigh over 200 kilograms, yet they can still be ridden safely. Some bicycles travel on tires with widths of no more than 20 millimeters, yet they remain safe and stable when in motion and there is no concern about simply tipping over. Both motorcycles and bicycles stabilize themselves when traveling at a suitable speed. This means that the rider does not constantly have to worry about keeping upright.
But how exactly does this work, what factors are required for it to be effective, and what forces are at work in this situation? One factor that affects the inherent stability of both motorcycles and bicycles is speed – both vehicles must be traveling at a certain minimum speed in order to stabilize themselves. The rotation of the wheels generates what are known as gyroscopic forces, which keep the system stable and return it to a stable condition for travel even when it is affected by external factors.
Another effect that helps stabilize two-wheeled vehicles is trail – the distance between the theoretical point at which the steering axis intersects the ground and the actual point at which the front tire touches the ground (see illustration, below). The larger the trail, the more stable the vehicle will be when traveling in a straight line; however, vehicles with large trails such as “chopper”-style motorcycles also require a larger steering force. A small trail makes a vehicle more nimble and agile, i.e. easier to steer, but such vehicles are also less stable and more “jittery” in terms of their response when traveling in straight lines at high speeds. When a two-wheeled vehicle tilts on its longitudinal axis, the trail exerts a force against the direction of the tilt at the point where the front tire touches the ground. For example, if a bicycle tilts to the right, a force will be exerted towards the left at the point where its front tire touches the ground, allowing the front wheel to turn to the right on its steering axis (in the direction of travel).
Both the trail and the gyroscopic forces keep bicycles and motorcycles stable when they are traveling in straight lines. In this situation, the two effects overlap. Due to the higher speeds they travel at, motorcycles usually generate greater gyroscopic forces than bicycles. At speeds of 25 to 30 km/h and over, a motorbike will stabilize itself, and would not tip over without a rider. On a bicycle, the trail plays a bigger role. In addition to the two aforementioned effects, however, stability is also affected by the shape of the bike, its overall mass, the distribution of this mass, and the width and shape of its tires. As such, all these factors need to be taken into account by designers and riders alike in order to help improve safety for two-wheeled vehicles – all around the world.