The Case for Power Assisted HPVs


A practical human power vehicle (HPV), as envisioned by the IHPVA (International Human Power Vehicle Association), might include weather protection for the rider (likely combined with streamlining to reduce aerodynamic drag), cargo and/or passenger carrying ability, safety features such as lights and horn, the ability to tow a trailer, and amenities such as a comfortable seat, fenders, electronics, and full suspension. The unavoidable result is a bicycle that is heavier and harder to pedal than a regular bicycle, especially up hills.

If most adults tend to pedal a simple bicycle slowly, and then for only a few miles, then it could be argued that for the proverbial average American a bicycle is of limited utility (maybe good for a ride around the campground after parking the RV), and a practical HPV is actually quite impractical.

No doubt there are some humans who can pedal an HPV as fast and as far as they like, but the average human simply can't or won't. If we want people, apart from a committed few, to use bicycles for practical conveyance in developed countries, then some concession may have to be made due to the inconvenient fact that most adults are out of shape.

The concession to be made is the addition of some sort of power-assist motor. The following chart helps to put human power into perspective. If the power produced by the average human seems low, consider that by definition half of all adults fall to the left of the curve below.  Also consider that while athletes often push themselves to exhaustion, average folk tend to stop pedaling well before reaching their absolute limit.

To see if human power is practical for powering vehicles, consider the following chart relating speed to power needed to achieve a given speed on flat land and on slopes while pedaling a light-weight bicycle,.


An average Joe or Jane, pedaling along at about 40 watts, will be moving at about 8-10 mph on flat ground with no wind. On almost any slope, however, the discomfort level raises rapidly (headwinds have a similar effect). If the vehicle is a practical one, meaning it's on the heavy side, then hills (or wind) soon become deal breakers. For pedal-power alone to be practical, one has to be pretty far out on the right edge of the human power bell curve.

Adding a small assist motor changes everything, however, making bicycles practical for a vastly greater number of people. Not that masses of people will suddenly start riding power-assisted bikes in the near future, but as the technology continues to evolve, the number of early adapters using it will increase. Then, once the technology matures and as the price of gasoline becomes ever higher, an alternative will exist for those who will come to need it.

Bicycle technology is mature, and most cities have developed bike paths and lanes for bicyclists to use. These cyclists, who have worked long and hard to carve out a transportation niche for themselves, often take a dim view of power-assisted bicycles, especially internal combustion engine (ICE) driven mini-motorcycles. Cyclists are naturally proud of their athletic achievements, of the years of training, practice, and hard work put into being in good enough shape to make bicycles a practical form of transportation and recreation. To slap a motor onto a cheap bike allowing the flabbiest to keep up with (or worse, pass up) the shaved-leg Lycra set on their several thousand dollar ultra light road bikes, seems a lot like cheating, especial if the flabby ones are using the pedals as mere foot rests.

The future of power-assist bicycles depends on there ability fit into the existing urban transportation ecology. If they become perceived as mopeds, primarily motor-driven cycles with token pedals, and have to be licensed, registered, insured, and forced to be ridden in traffic instead of using bike lanes, then they really have no future. If perceived as primarily bicycles for those who, through no fault of their own, are handicapped by no longer being young and fit, and can coexist with pedal-powered vehicles using the same bicycle transportation infrastructure, then they have a future, possibly a very bright one.

The sensibilities and sensitivities of the millions of existing bicyclists needs to be considered. For bicyclists and other users, multi-use bike paths are havens from the surrounding and dominant ICE traffic. Having 2-stroke machines buzz past them, pedals fixed, spewing exhaust fumes is a slap in the face, and not likely to be tolerated.

ICE assist motors for bicycles have been around for decades, the technology has not evolved greatly and isn't likely to. While cheap and having unlimited range for the price of a fill-up, the ICE assisted bicycle is a technology on its way out. The new, rapidly evolving technology on its way up is that of the electric motor-assisted bicycle (ebike).

Ebikes have been around a long time also, but have been burdened (literally) by having to carry around bulky and oh-so-heavy lead-acid batteries. As battery technology evolves, as it rapidly has been in recent years, ebikes are (literally) poised to take off. As batteries continue to grow smaller, lighter, yet more powerful, efficient, and eventually cheaper, ebikes will eclipse ICE bike technology. All vehicles may someday be electric vehicles, and it makes sense that bicycles, the most efficient form of transportation ever developed, will be the first to successfully go electric.

An essential element of the ebike concept has to do with speed. If the speed is limited only by the power of the motor and the sanity of the rider, then ebikes going at 30+ mph, blowing past non-bionic bicyclists, will not be able to coexist with, or be accepted as, bicycles, but will be seen as motor vehicles to be regulated as such. What then is the line dividing bicycles with power-assist from motor vehicles? Well, in the USA, the federal government has already decided the matter. Power your bike at over 20 mph and you're a moped, over 30 and you're a motorcycle, but keep it under 20 mph and you're a bicycle.

Such a speed is actually just about right. It is twice the speed most people could or would pedal a bike for any length of time, yet slow enough to remain safe, and for the sake of the all important human ego, not so fast that most human-power-only cyclists couldn't pass an ebiker if they felt like it. Quiet electric motors, no fumes, no noise, and moderate speed are the ticket to gaining acceptance from other cyclists provided, of course, the ebike really is a bicycle that can be ridden effectively without the motor on, with real functional pedals that are actually used to power the bike most of the time.

The great benefit to the out of shape masses is that by pedaling within their comfort zone, they will gradually become fitter, use the motor less, cycle more, and go further while loosing weight and building up both muscle and ego. For every less car on the road, both society and the environment benefit. As ebikers join the ranks of bicyclists, support for the development of bicycle pathways and infrastructure will grow. It rather looks like a win-win scenario for all concerned.

The acceptance of ebike technology is not progressing smoothly, however. Ebikes, lumped in with ICE bikes in the public mind, and opposed by political special interests, have been banned by some states and cities, if not outright, then banned from using bicycle paths.

Such setbacks need to be reversed. The federal laws governing ebikes (ebikes must have functional pedals, a motor under 750 watts, and a speed under 20 mph), needs to be universally accepted. If every city or state makes up its own more restrictive rules, the market for ebikes will not grow, their future will be dim, and the potential benefits of ebikes will be lost.

Ebikes can take the place of a car for relatively short intra-city trips with obvious financial, environmental, and health benefits.  Ebikes allow people to exercise without being forced to overexert themselves; they're like exercise bikes that actually go somewhere.  There are times when even the most committed pedal-power-only cyclists will have to dress up and want to get somewhere without being drenched in sweat.  Ebikes are great equalizers that allow people of varying abilities to go places together without forcing the stronger riders to pedal along at an unbearably slow pace.

To better appreciate the impact of ebike technology on society and the issues that citizens need to consider, an analogy might be helpful. Let's imagine someone invents electric powered leg-assist devices (elegs) that humans no longer in their prime could put on like trousers (but just a bit bulkier). One would be able to tell someone was wearing them, but only on second glance.

Elegs would enable parents and grandparents to go on long walks, even go on mountain hikes, with their progeny without slowing them down. Octogenarians could stroll around town, go shopping, walk their dog, and otherwise enjoy a level of mobility they had known in their youth. And who would want to ban such a wonderful technology? Who would condemn others and themselves (when they themselves grew old) to unnecessarily shuffle slowly along from place to place?

Well, as with all new technology, there would be problems. If elegs could enable the weak to walk at a normal pace—at the same speed they could when they were young and fit, then it would only be a matter of time before elegs would enable them to walk at the speed of an Olympic racewalker (about 3-4 times normal walking speed). Now octogenarians plowing through pedestrians, leaving them in the dust, would become a problem. And of course every 12-year old will want elegs too! Then you'll hear a loud reactionary cry to ban elegs from all parks, sidewalks, and public places.

Should elegs then be banned? Or should we instead define the constraints under which those using elegs should operate? The general idea would be that those with elegs, when walking anywhere other pedestrians are, should be content to not walk conspicuously faster than their non-bionic brethren, which is to say about 2 mph. If those with elegs limit themselves to 2 mph, then they should be considered pedestrians, able to coexist with other pedestrians, and allowed to go anywhere those with two good legs are allowed to go.

Should we force manufacturers of elegs to cripple them in such a way that they are incapable of assisting a person to walk faster than 2 mph? Surely there are situations what even the most responsible person might need to go faster than 2 mph (such as to escape a danger). Many could use elegs to advantage, and their doing so should not be prohibited. What should be prohibited is the irresponsible use of elegs to put others, the normal pedestrians, to a disadvantage. It would also be reasonable to prohibit children (those not truly handicapped) from using elegs since their use by the young would interfere with normal development and eventually make them handicapped and dependent on elegs. The fit, or those who could reasonably become fit, should not be encouraged to use elegs, but then the cost and a 2 mph limit would take care of that.  Society would hopefully find a way to embrace elegs while minimizing any possible negative impact of the technology.

By analogy, then, society should allow ebikes that are not ridden conspicuously faster than other bicycles (<20 mph) to be ridden anywhere unassisted bicycles are allowed to go. While no ebikes should be optimized to go faster than 20 mph, neither should they be required to have automatic cut-off switches to prevent them going faster than 20 mph under any circumstance. In crossing a narrow, high traffic bridge without a bike lane, for example, it would be much safer to keep up with the traffic rather than block traffic or tempt cars to pass with only inches to spare. While doing so would pull high amps and drain the battery inefficiently, sometimes "speeding" is the prudent thing to do just as in a car a driver can legally, though briefly, exceed the posted speed limit while passing another vehicle on a two-lane road.  In some situations ebikes would be safer than unassisted bikes.

Ebikes are an immanently sane and practical transportation option provided some limits are set. Such limits have been set by the US Federal Government, and the 20 mph limit is even reasonable. All that's needed is for states and municipalities to go along with federal law and regulate ebikes the same as bicycles. Ebikes might best be viewed by the public and government officials as bicycles for those handicapped by not being athletic. Someday, even Lance Armstrong, if he lives long enough, will have to give up cycling or get an ebike. That being the case, only those expecting to never grow old would even think about banning ebikes. A better idea would be for society to prosper through the use of ebike technology.

Related articles:

Ebike Design: How much power is enough?

The eTrek: A practical eHPV

Ebikes as Exercise Bikes

Power vs Slope


Related links:

Ebike Touring Association


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