Roads

and the road’s length. Smooth roads reduce the power vehicles need to maintain their speeds by reducing surface-tire rolling resistance. Environmental engineers therefore design durable roads that can carry heavy loads without cracking or wearing, yet give vehicles a smooth driving surface. Asphalt and concrete meet these needs but they also affect the environment in negative ways. Asphalt comes from the crude oil refining process, so it consumes nonrenewable fossil fuels, and the production of concrete’s main ingredient, cement, accounts for 7 to 8 percent of the world’s carbon dioxide emissions. New road building in sustainable communities will therefore focus on three areas for improvement: (1) alternate road materials; (2) road planning; and (3) road use.

Road planning and design work hand-in-hand with alternative materials to reduce roads’ carbon footprint. For example, gas-wasting designs such as long cloverleaf entrances and exits on freeways can be phased out and replaced with shorter but safe entry and exit lanes. Newer roads also improve water conservation with drainage ditches that catch runoff and
channel the water to wastewater treatment plants. Future road materials may soon be used in which a porous surface allows rainwater to seep into the earth and thereby reduce the burden on treatment plants.

Road planning also involves study on the ways people use roads. Commuters today follow very different driving patterns than commuters of a decade or two ago. The U.S. Department of Transportation’s Bureau of Transportation Statistics (BTS) has conducted a study that related a region’s economy to driving patterns. The BTS found a recent rise in the
proportion of daily “stretch commuters” or “extreme commuters,” meaning they travel more than 50 miles (80 km) each way to work every day in trips that take 90 minutes or more. Stretch commuters make 19 out of 20 of these trips in personal vehicles rather than mass transit. Housing costs have often contributed to these lengthening commutes due to the “drive until you qualify” syndrome. The MSNBC reporter Allison Linn wrote of a familiar circumstance in 2008: “For Dollie Kinkead, the economic turmoil gripping the country translates into an 80-mile [129 km] drive each workday from a house she can’t sell to a job she thinks she’s lucky to have.” Environmental engineering can help alleviate this bleak picture, but factors in society obviously play competing roles.

Long commutes may not be as fixable as finding new technologies in road building and planning. Austroads is an association of Australian and New Zealand road and traffic experts that takes a three-pronged approach to road-planning: (1) drivers’ needs; (2) economics; and (3) the environment. This organization wants to foster sustainable roads, meaning
roadway construction that reduces resource consumption, improves landscape and air quality, does not cause water or noise pollution, and

The typical combustion engine converts gasoline to motion efficiently at speeds higher
than 35 miles per hour (56 km/hr) with steady driving to avoid fast accelerations. Fuel
efficiency decreases in many cars at higher speeds.

protects habitats. Austroads has taken on all of these goals while providing resources for building quality thoroughfares for drivers and mass transit. Austroads’s chairman Alan Tesch explained in the organization’s latest annual report (2007–08), “A total of 41 projects were completed [in the past year] and 29 research reports and technical reports published. There were also 15 guides published . . . The guides are intended to be used by road authorities in Australia and New Zealand as a complete package of technical information that applies a consistent standard to road building . . .” Austroads also offers technical resources on road
design, planning, maintenance, and operation.

In the United States, engineers have reexamined two road designs: cloverleaf interchanges and traffic circles. A cloverleaf contains four loops and one or two bridges called overpasses that enable drivers to switch from one roadway to another without stopping at a traffic light. These designs decrease time spent idling at lights, but they also lengthen driving distance.
Traffic circles (called roundabouts in other countries) allow traffic to flow without stopping at interchanges between two or more roadways. Circles have offered an efficient traffic control device for many years until the 1980s when heavy traffic overwhelmed many circles. Densely populated New Jersey, for instance, once depended on more than 100 traffic circles statewide to ease traffic flow, but the state has gradually removed many of its busiest
circles that slow traffic rather than speed it up.

Environmental engineers today develop ways to
decrease fuel waste while maintaining safe roads.
This interchange in Fort Worth, Texas, in 1958,
seemed like a well-designed answer to navigating
the country’s new interstate highway system. This
design called a cloverleaf, however, requires extra
driving and road-building materials so it may not
be the best choice for helping the nation reduce its
total fuel consumption. (TexasFreeway.com)