Why can’t cars keep rain and snow out?

Today’s cars can park themselves, connect to your smartphone and warn about traffic in your blind spot, so why can’t they keep snow and rain from pouring onto your head when you open the door?

Blame a combination of fashion and fuel economy, but help could be on the way.

For decades, cars had “drip rails” along each side of the roof to protect your head, upholstery and sanity from snow and icy water.

“Drip rails or rain gutters used to be de rigueur on all automobiles,” said Matt Anderson, curator of transportation at the Henry Ford Museum in Dearborn, Mich.

“They started to disappear in the mid-’80s. It was a concession to styling and fuel economy and reducing wind noise,” Anderson said, “but you do get snow on the seat and rain falling on your head.”

The change made cars more attractive and aerodynamic, said Peter Davis, vehicle design chief for consultant Tata Technologies. The rails on the roof disrupted air flow and altered the car’s profile.

Getting rid of the rails improved fuel efficiency and reduced wind noise.

The advent of one-piece body sides also contributed to the drip rail’s demise. Using a big single piece of metal for the entire side of a vehicle eliminates squeaks and gaps between body panels, but it also got rid of the gutter’s spot where the panels met.

Aesthetics and aerodynamics also drove a move from vehicles with vertical sides to windows that angle inward and doors that wrap up into the roof. That creates another opportunity for snow or rain to fall into the car by moving the opening where the door and roof come together so snow falls onto the seat rather than to the vehicle floor.

The 1986 Ford Taurus was the beginning of the end for drip rails. Acclaimed for its aerodynamic “jelly bean” look, it rewrote the book on the American family sedan. When the ’89 Honda Accord followed without drip rails, the die was cast.

Ford hopes the 2015 Mustang coupe and convertible will reduce the problem when they go on sale late this year. Both have roofs designed to direct water away from the doors and windows.

“We added a V-shaped insert” along the edge of the convertible’s fabric roof, Ford engineer Andre Beduschi said. “It acts as a trough to wick water away. It performs much better than our current convertible roof.”

The Mustang coupe’s metal roof has little ridges along its outer edges that channel water to the front and rear of the car. “The sheet metal and offsets and moldings in the doors were developed to keep water from pouring in,” Ford engineer Ron Lovasz said.

Features like that may reduce the amount of rain that gets into cars, but snow will remain an issue as long as the sides of cars continue to slope inward to the roof and use one-piece metal stampings.

The best advice may be to keep the snow brush handy and brush the roof off before you open the doors. Be warned, though: the trunk has even less protection to keep snow out than the doors.

It’s been that kind of winter: Resistance is futile.

Mark Phelan is the Detroit Free Press auto critic. He can be reached at mmphelanfreepress.com.

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