The Maxi Taxi concept describes the advantages of convoying in saving fuel during highway travel. Cars that closely follow each other can achieve impressive reductions in total air drag. Air drag is the leading overall drag component at higher speeds and therefore represents the lion’s share of a car’s fuel consumption at speed.
Air drag is a complex subject, and the original maxi taxi concept aimed to reduce overall air drag by fitting a number of cars as close together as possible and thereby to create a drag profile that is similar to a railroad train, which is basically a flexible tube that is being dragged through the air. We can achieve a similar effect with car convoys and the cars do not have to be the same, but equal width would be real a benefit.
In 1522 a sailing vessel, named the Victoria, arrived in Spain and thereby completed the first circumnavigation of Earth using only sustainable power (wind). This voyage is generally called Magellan’s voyage, but the person who completed the voyage in command was Juan Sebastian Elcano.
Since that time, humans have circumnavigated Earth in any number of novel fashions including rockets, aircraft, and submarines, but with the exception of a balloon circumnavigation (Picard and Jones, 19 days, 1999), which is more akin to drifting with the wind rather than navigating, all those novel methods used fossil or external fuels in some fashion.
By water we have copied the Magellan feat any number of times using solar cells or much faster sailboats, and greatly improved on the circumnavigation time. The record for a sailing circumnavigation is 45 days and the record for a solar waterborne circumnavigation is 584 days. Not bad, noting that the original voyage took 4 years but these feats are really improvements on a method rather than a novel approach.
Only this year, almost 500 years later, are humans attempting to take a new approach.
Powering cars with solar cells installed on the car is an intriguing proposition, but unless we drive for very high efficiencies with resulting uncomfortable and impractical cars such as solar racers, it will probably not be possible to power cars with solar cells to the extent that we power cars with chemical fuels such as gasoline, diesel, LNG or hydrogen. We will probably stick with chemical fuels since hydrogen is an almost perfect fuel and can be generated with electricity generated by solar and then loaded aboard a car as a fuel with zero emissions and long vehicle range. As long as we develop a hydrogen infrastructure, from a technological point of view, we do not have to worry too much about outfitting cars with massive solar panels.
On the other hand, to be on the move completely under own power (slow but unlimited range) is a unique proposition. At sea to be under own power is easy by using sail. To be under own power on land is a little bit more difficult. Historically we sort of did it before, by using oxen to pull Conestoga wagons. The fuel for the oxen was the food that could be found along the way. In effect, a pioneer trip across the United States was driven by careful route management of forage and water opportunities.
This leads one to think if it would be possible to fit out a Maxi Taxi with solar panels and to be able to travel across the United States in relative comfort completely under own power. Hannah and I ran some numbers and, surprisingly, it is not at all that difficult.
Some people pondering five foot wide roads (or, at best, roads a little wider than 60 inches) populated with Maxi Taxis may think it would spell the end of driver excitement. Personally, having owned a Triumph Spitfire (57 inches wide) and always having coveted the original Mini Coopers (55 inches wide), I doubt that is actually the case. At the very least, the Maxi Taxi lanes provide sufficient width for motorcycles, and, remarkably, automated driving will make motor cycle riding safer since automated driving will be more effective at dealing with motor cycle traffic than human drivers (motor cycle accidents are often caused by car drivers who are not aware of the motorcycle presence).
But for more Maxi Taxi system compatible cars, which, at the same time, are more exciting than just about any car available today, an excellent example is the “Carver” car, developed by my Dutch boyhood friends, Peter and Chris van den Brink.
In our office, we often discuss the pros and cons of new tech. So when Elon Musk’s new Hyperloop preliminary design study came out on Monday, it was an obvious source of discussion.
While some of us (*cough* Rik) have some doubts about the Hyperloop concept, we can agree that a very attractive design could be reached by incorporating the Hyperloop and Maxi Taxi design concepts into one (see Rik’s blog entries about the Maxi Taxi concept on the M&O website – a summary can be found here).
With the Hyperloop’s potential advances in speed, and Maxi Taxi’s pillars of standardization and door-to-door public transportation, there is potential for a commuter’s dream. In the joint concept, a standardized carpooling taxi design that is road-worthy and Hyperloop-worthy could enter the Hyperloop and be transported at high speeds to another city (the sweet zone is a city that is several hundred miles away by Musk’s estimates) where the taxi would disembark the Hyperloop and drop off passengers at their destinations within the city.
Not too long ago only a small proportion of humanity had access to vast resources (which actually equates to access to energy). Although the very rich could travel by ocean liner between continents, poorer people’s action radii were very much smaller. For most of humanity’s existence a human might be tied to a very small patch of ground, which was accessed by walking. There were nomadic tribes, but even those tribes moved slowly and seasonally. Somewhat more recently, sailors started to move over vast distances, but they did so on a commercial level and not on a personal level.
Today, a much larger proportion of humanity travels much more, and over much longer distances. This is due to low cost and readily available energy. While this makes life interesting, it is also an efficiency trap and Maxi Taxi, instead of reducing energy use, may simply increase our mobility for the same energy dollar and not result in overall energy savings.
Automated driving is central to the Maxi Taxi concept. Although the Maxi Taxi ferry concept does not specifically require full automated driving, the ferry concept, at a minimum, will use automated parking type technology to load and unload the ferries automatically with human drivers on public roads. However, the Maxi Taxi concept will really come into its own with automated driving.
Automated driving is probably the most radical component of the Maxi Taxi concept from a consumer point of view.
I have been closely following automated driving efforts for over 15 years, and today we are far past the proof of concept phase. As a matter of fact, there are no technological barriers to automated driving and the remaining barriers are related to manufacturing, standardization, and regulatory issues and consumer acceptance.
This is our third blog on the Maxi Taxi concept, for earlier blogs on Maxi Taxi go to:
The Maxi Taxi concept has chosen five feet as the working standardization width for the system, which would result in road lane widths of about 6 feet. This is a nice return to more traditional road widths, noting that the narrowest roman roads were 5 ½ feet wide (and double lanes were about 13 ½ feet wide).
It is possible that the arbitrary width of five feet is not the exact optimal width, but chances are it is pretty close for quite a number of reasons.
Five feet is a pretty normal width for passenger cars, even though we can choose to design and built passenger cars with widths between less than 2 feet (when thinking in terms of motorcycles) up to 8 feet and possibly a little more. Today cars are generally wider than five feet, for quite a number of reasons, many of which are esthetic. While it is fun to design attractive cars, the Maxi Taxi concept aims for maximum utility and efficiency for transportation although, hopefully, the end result will have some level of attractiveness. read more »
The April issue of (mt), the SNAME house magazine, will feature an article by Dr. Wayne Neu, professor of Aerospace and Ocean Engineering at Virginia Tech. Dr. Neu updated the classic 1950's Gabrielli - von Karman plot using more recent vehicle data collected by the students in one of his classes.
The Gabrielli - von Karman plot is one of those devices that allows one to think in terms of the real big picture. In essence, it plots vehicle drag over lift against vehicle speed. It is a cornucopia of transportation devices and allows one to compare one mode of transportation against another as far as basic efficiencies at various speeds is concerned.