Archive for June 2nd, 2009

If time permits I’ll be attending this entry at this year’s New York Science Festival (I’ve interviewed all three of the participants).

From Insects to Interstates

Anna Nagurney is the John F. Smith Memorial Professor in the Department of Finance and Operations Management at the University of Massachusetts, Amherst. Her research focuses on congested transportation networks and their relationship within different systems ranging from the Internet to global supply chains to electric power generation and distribution networks.

“While in 1983 a pothole would need to be over 3 inches in depth and over 30 inches in
length to pose a rim damage threat to even a mini-compact vehicle, in 2006 holes as shallow as
1½ inches no more than 16 inches long could, in theory, cause rim damage.”

That’s from Influence of Road Surface Discontinuities on Safety: State of the Art Report, a new TRB circular.

The reason is “plus-size tire rims,” a form of road social signaling that basically says, “I’ve got money to spare on rims” that will soon need to be replaced.

“The principal disadvantages [of plus-size rims] are many and include cost, weight, fuel economy, ride quality and wet grip/snow traction, as well as indicate hydroplaning resistance. Perhaps more serious downsides include reduced load-carrying capacity at extremely low aspect ratio, a shift in the handling balance toward oversteer and a slight increase in rollover propensity. A further disadvantage is that the increased vertical stiffness of low aspect ratio tires means they act as shock transmitters rather than shock absorbers. Safety implications arise when a motorist will agree to replace a bent wheel that is no longer able to hold air, but will continue to use an injured tire since the damage is internal and not visible to the naked eye.” (Walter, J. Style Over Substance. Tire Technology International, March 2006.)

The authors also conclude, by the way, that potholes have little negative effect on road safety.

And one last thing: The vehicle brand above is now the property of an obscure Chinese company. Will they still be adorned with all those ultra-patriotic bumper stickers?

Reading this article about “intelligent speed adaptation” — or devices that limit speeds according to the posted speed of the road (imagine that!) — in Australia (where most of the ISA research is being conducted), I was curious about this phrase:

In cases of emergency there is an override system whereby the driver can either flick a switch or floor the accelerator to disable the safety device and put the car back in manual control.

The immediate question that springs to mind is how long can the device be disabled for? Would drivers not simply disable it for their entire trip? Is ISA meant to be a merely advisory technology, a bit of feedback to discourage speeding, or an actual enforcement mechanism? I tend to think the whole issue of hypothetical speeding for some emergency is a bit overblown (when compared to the potential safety benefits of ISA) — for something like crash avoidance, braking is typically just as valid a response. On the other hand, there are moments on Australian roads, as in the photo above, where a bit of speed might be desirable.