TvA entered the AXP based on the rules that were proposed at the time. Our entry focused primarily on
achieving efficiency via the use of a streamlined narrow vehicle with innovative steering/ stability
systems. The "efficiency" of a vehicle depends largely on the way it is used . Because most vehicles
carry less than two persons a wide car with space for 4 people results in a waste of energy over its
operating life. Typically a motorcar carries one person for 90% of its operating time. Also, wide/ large/
heavy vehicles are fundamentally inefficient requiring more space to park, more road to drive upon and
more raw materials to produce.
Narrow vehicles can solve these problems. However narrow vehicles require innovative control systems
to allow the driver a simple control interface [ simple steer] but also allow the vehicle mass to be shifted
to the inside of the corner automatically unlike a motorcycle where the driver "balances" the vehicle
mass[ manual countersteer].
The AXP organisers stated from the beginning their intention to ban vehicles that required "balancing
by the driver" TvA agreed with this because we have always maintained that a vehicle to replace the
motorcar should retain motorcar control techniques. To expect the driver to have "balancing skills" as is
the case in a motorcycle is not realistic.
So, TvA entered into the competition because we believed we had a very efficient vehicle that could win.
Our vehicle complied with all requirements within the rules and our entry was welcomed by the AXP.
However after the CONSUMER UNION became a partner in the event additional rules were inserted at the
"last minute" to say that "all 4 wheeled vehicles must have a SSF[ static stability factor] of 1.3" This
rule applies to all 4 wheelers in mainstream or alternate class even if they shift their mass
advantageously during cornering and so gain stability independent of their SSF.
This fits with the CU campaign against SUV rollovers in the USA. The CU is not without criticism in its
The imposition of the "4 wheel SSF" rule in a blanket fashion without any understanding of "automatic
stability systems" throttles innovation . The TvA vehicle would have proved as stable as any vehicle
[ no matter how wide ] in any dynamic testing... and we wanted to show this to be the case to all.
A conventional motorcar leans the wrong way and so looses stability as it corners whereas the TvA
system tilts inwards in a corner and so gains stability. To require a SSF of 1.3 for a tilting vehicle lacks
logic. This rule remains in the final draft and so the TvA entry [ a 4 wheeler] is banned by the AXP rules.
But furthermore, if TvA had entered a 3 wheel version of its system and not the 4 wheel version then the
"4 wheel SSF" rule would not apply and the vehicle would be accepted under the rules.
Other anomalies arose because in the AXP rules a motor vehicle with 4 wheels is required to have a
SSF of 1.3 but a 3 wheeled motor vehicle [in the alternate class] is not tested for ANY static stability.
Generally speaking a 3 wheeled non tilt vehicle is less stable than a 4 wheel non tilt vehicle and a "SSF"
is often used to ensure that 3 wheel NON tilt vehicles are stable in various jurisdictions Worldwide.
The thrust of the AXP rules attempts to reverse this logic.
These irregularities within the rules reflect a poor grasp of what is required in a competition of this type.
Its not that I seek to be excessively critical but the point remains that TvA warned the rule makers within
the AXP of the problems they were about to create. A solution was presented to the AXP but ignored.
I wish the competition well. TvA wishes the competition well. We applaud any attempt to highlight the
need for efficiency. However there seems to be some lack of efficiency within the AXP team that has
resulted in a less than ideal outcome. I suspect this was inevitable.
Hopefully my comments will be seen as constructive and better outcomes in future events may result.
Please note the extract below is from the latest rules issued by the AXP. Click here for the full details.
Phillip James [TvA Australia] www.tiltingvehicle.net
A comment on the Automotive X Prize...
YES [ TVA agrees]
NO [ TvA agrees]
YES [ TvA agrees
YES [ TvA agrees]
YES [TvA agrees]
YES [TvA agrees]
NO [ TvA DOES NOT AGREE] The
requirement for a narrow track tilting vehicle
to have a static stability factor of 1.3 suggests
a lack of understanding of vehicle dynamics
and contradicts all innovation in this field
where vehicle stability is enhanced by actively
tilting the vehicle mass relative to the road
|UPDATE 2015. A few years have passed with no change to the USA system of vehicle classification.
Its interesting to observe the rules and the outcomes that they are creating:
The 3 wheel non tilt vehicle [ above] is legal in the USA. The mass distribution is flawed and the vehicle
would be unstable when cornering but this does not concern the regulators in the USA. On the other
hand the 4 wheel vehicle [ below] is banned in the USA even though it is clearly fundamentally more
stable and safer than the example above.
The second vehicle [ renault twizy] is banned because?.... it has 4 wheels and cant comply with the
regulations that apply to large cars, even though the extra wheel makes it far more logical as an
urban commuter than the first vehicle which having 3 wheels needs no testing !
The UNECE are taking steps to harmonise vehicle regulations so that the requirements are NOT
based on the number of wheels that a vehicle possesses and TvA will only design to those
regulations. Phillip James 2015