The challenge: Great design that satisfies the law

Have you ever looked at a new car and spotted something that was just plain wrong?

Aesthetically wrong, that is.

Maybe the door cuts are a fraction off, or the hood line is too high. You ask yourself: How could the designer not see that?

Chances are he did and was pulling his hair out about it. But these days designers' talents are being pitted increasingly against global crash and safety regulations and the desire for aerodynamic efficiency.

The quest to create a beautiful form while meeting the letter of the law is a huge challenge.

"When we start with the design, there is a bit of guessing about what the legal text actually means," says Michael Mauer, head of Porsche Design Studio. "Then the engineers give us the hard points. Sometimes it looks horrible, so we have to start over and try again."

For instance, pedestrian-safety regulations require a certain amount of deformation space between the hood and the engine. That can ruin any idea of a sleek hood line.

"The pedestrian protection challenges are huge," says Clay Dean, Cadillac's design director. "The bull nose, the upright look of the front fascia, the lower kick-point for the bumper are all about pedestrian protection."

Luxury automakers, with more cost flexibility, are engineering "active" hoods. In a pedestrian-vehicle accident, an active hood pops up to cushion the blow to the pedestrian. Under normal driving conditions, there is a sleek hood line.

"But," Mauer says, "the cars in smaller, cheaper segments can't afford these high-tech solutions. They have to compensate in the form of the car, which results in bad design. We're seeing hoods that are 80 millimeters [about 3 inches] too high."

And in the world of car design, where, Mauer says, "we are fighting for millimeters," 3 inches can send a car designer back to the drawing board.

Ian Callum, Jaguar's design director, says: "Pedestrian impact is such a difficult issue to analyze in dynamic terms.

"There is a set box of metrics that you have to observe. You have to create a shape to meet the spirit of the legislation without sacrificing your design aesthetic."

Laws in different parts of the world often conflict, making the designer's job even more frustrating.

For example, to meet European regulations that rule the driver's field of view, the hood must fall below a sight line -- the so-called eye ellipse -- struck four degrees downward from a 5-foot-tall woman's eye point.

"That's a tough one to meet." Callum says.

Meanwhile, because of the increased rear-vision requirements, larger side mirrors are needed. But that increases the vehicle's aerodynamic coefficient of drag and thus increases fuel consumption.

It gets worse.

Car designers love narrow glass greenhouses because they make vehicles look sleek. But North American "unbelted occupant" laws dictate the minimum height of the car's header -- where the windshield meets the roof -- which then conflicts with the European eye ellipse regulations and others.

"The worst is the head impact regulations on interior design," Mauer says. "Crisp, high-level design means there are small shut lines (between the panels and doors) and tight radii between forms.

"But we can't do that," he says. "The regulations mean we have to soften the interiors, and we lose that precise impression we want the interiors to have."

Meanwhile, Cadillac's Dean says, Europe's move toward six-star crash test safety means an automaker with only five-star ratings will be seen as less capable.

What will earn that sixth star? Among other things, forward radar pre-collision systems. That hardware takes up a lot of space.

"Underneath the hood is already crowded, but those controls have to go somewhere," Dean says.

Then there are the new safety guidelines that will test "overlap" impacts -- headlight shearing an oncoming headlight. That sort of crash energy is harder to dissipate through traditional frame rails. Usually, such a crash will just destroy the suspension and tear the door off its hinges.

For the redesigned Accord, Honda created an additional side member and an upper frame, says Dave Marek, director of design for Honda R&D Americas. But that additional structure required some intricate shaping of sheet metal to avoid a clunky fender shape.

Then there are cases in which a country has laws that make sense only for that country. Still, the rules affect global design decisions.

Canada requires 15 millimeters additional rear-tire coverage to keep stones from being kicked up behind the car. Some automakers flare the sheet metal of their wheel arches to comply, while others just slap a plastic extension at the bottom of the rear wheel arch.

"There must be common sense in making these regulations," Jaguar's Callum says. "Physics are the same in Europe, the U.S. and Australia."

Sometimes, the laws for one type of vehicle are different from those for another type, which can affect design, Porsche's Mauer says.

"We were doing the hood [cut] lines for the Cayenne, and I wanted it to have a hood line just like the Panamera. So I sent the clay model in, and the engineers sent it back with a 'red dot' on it because there is a requirement for the hoods of SUVs that there isn't for cars," Mauer says.

As a result, the hood cut had to be narrowed on the Cayenne. Compared with the Panamera or 911, it looks much less like a traditional Porsche. But Mauer had no choice.

Meanwhile, increased fuel economy regulations have automakers looking for slippery designs. But they can come with their own tradeoffs.

"We wanted to avoid the visible spoilers on the Panamera Turbo. But we needed them because at 300 kph the car starts to fly," Mauer says.

The down-force solution was to have a retractable spoiler. But that cost money because of additional engineering time and parts costs.

Honda's Marek says: "Regulations are our lot in life. You have to choose your battles.

"You have to be able to say, 'We can live with that.' But I never want to make the excuse of 'We had to do it this way because of this regulation.'"