As a surface for wheels, tarmac does its job well enough. Tarmac is flat, smooth, and solid (usually). But there is a price we pay for the convenience of paved roads and parking lots everywhere—a price paid in heat, noise, and polluted runoff. We went in search of better pavement and found these potential solutions.
Who says it has to be black? As anyone who has walked across a scalding driveway at the height of summer knows, tarmac gets uncomfortably hot. It's not just bare feet that get burnt—all those car parks baking under the sun contribute to the urban heat sink, making cities even more unbearably hot. A few years ago, Phoenix decided to paint some of its parking lots a light shade of green in order to reflect rather than absorb heat. Emerald Cool Pavement's pastel pavement coatings are supposed to keep the surface cooler.
By paving over roads and carpark, we've created huge swaths of impermeable land. And the water that washes off roads and car parks is rife with oil, salt, fertilizer, various -icides, and heavy metals that eventually end up in our waterways. Permeable asphalt lets water pass through while trapping pollutants in its porous matrix. In the U.S., it's recommended for low-volume roads and car parks, but permeable pavement has also been successfully used on motorways in pilot projects.
Demonstration of a permeable paver. JJ Harrison/Wikimedia Commons
There's another upside to permeable pavements: noise reduction. The same porous structure that filters pollutants from water also absorbs sound. That means a quieter ride for drivers and motorway neighbours alike. It also reduces the need for the unsightly sound barriers that surround motorways.
If you're familiar with non-Newtonian fluids, you've probably seen someone running on it or punching it or riding a bike across it. Non-Newtonian fluids are pretty damn cool, and they seem to defy the laws of physics. The same principle that makes for cool videos makes non-Newtonian fluids good pothole fillers: the material is usually liquid, so it conforms to the shape of a pothole, but it turns solid with a sudden force, like a car driving over it. A group of students at Case Western University invented a fluid-filled bag that can be dropped into potholes as temporary fixes while waiting for a construction crew.
Lead image: Reflective pavements via Emerald Cities USA Ltd.