Collaboration questioned

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Automotive testing examines the performance of a vehicle, or some portion of it, in a particular condition that approximates a real-world environment. The results of the testing give us an indication of how the vehicle will perform in real life.

Test procedures are developed and established based upon engineering experience, theoretical understandings and real-world observations. New developments observed in the world are ultimately reflected in updated test procedures for future product development cycles.

An interesting engineering, testing and development challenge arises when parallel complementary product universes exist, and significant developments and investments are made in each. Progress should proceed with some understanding of where the other universe is going. Yet often, communication and understanding between universes seems more accidental than purposeful.

Passenger vehicles have changed over the years. Has road design changed enough to keep up with vehicle architectural and performance changes? Let’s look at the mechanical interrelationship between vehicles and roads.

A simple example we see all the time is when vehicle fascias scrape as drivers park by feel and drive until the front tires contact the curb. Car fascias have become lower for aero and styling reasons, but US parking curbs remain high. Fascias have become the architecture of choice over chrome bumpers, but parking curb designs have not changed, hence a minor collision between universes.

On a more serious note, do road and vehicle architectures complement each other? Are the two universes developing along complementary paths?

Recently I witnessed a serious rollover on a US highway in the Detroit area, where an SUV barrel-rolled multiple times after impacting the center median.

The concrete center divide typical of US highways is built with sloping sides, including a flatter slope toward the wider base. The medians were designed in the 1950s and 1960s to minimize vehicle damage and keep the car from bouncing back into other vehicles. Speeds, however, were slower and vehicles were different then.

In the not-too-distant past, front tires were shielded by a metal structure in front and tended to be indented relative to the vehicle sides. These days, the corner structure before the front tires is often no longer metal: it is a plastic fascia covering a short bumper beam, and the front tires are pushed out laterally to the edges of the wheelhouse. Often the vehicle’s front tire corner can be seen when viewed from the front. It looks great, but does it work with the inclined road median?

When you build a rock buggy, you put the tires at the corners to expose the front and side of the tires, because you use the tires to climb walls and obstacles.

Driving around Detroit, there are hundreds of tire marks on the concrete walls along the submerged highways. These walls are the typical, double-slope median in some places and are pure vertical in other locations.

On the sloped walls, a tire mark will often travel vertically up a meter or more. It’s especially prevalent where the inclined median is on the outside of the curve and the vehicle impacts it at a more aggressive angle than a simple straight sideswipe. How close is that tire path to a rollover, one of the most dangerous accident types?

On the other hand, you do not see the vertical tire vector associated with the inclined medians where the concrete wall is vertical. No vertical vector, so less tendency to roll over.

So do we have complementary universes between vehicles and roads, or are the vehicle and road universes diverging? Was testing done to confirm that the sloped center median is appropriate for today’s vehicle architectures? Does testing consider the more aggressive angle observed in road curves? Do vehicle designs consider the potential to ‘ride up’ the median?

Our automotive industry has a wealth of knowledge and experience regarding vehicle safety, crash performance and survivability. Our road design professionals have a wealth of knowledge and experience regarding road median design. It would be interesting to know if the road people talk to the car people.

In researching this subject, I came across the research paper Development of a TL-5 Vertical Faced Concrete Median Barrier Incorporating Head Ejection Criteria. Published in 2007, it has 82 references related to road median design and construction. Obviously a significant amount of thought and research has gone into the understanding of road barriers. Now, if we can focus our vehicle design, road design and road construction forces toward common understanding and mutual progress, we could achieve amazing results.

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