Active traffic management (ATM) uses advanced technologies (computing, communication, and electronics) and traffic management centers to improve roadway traffic flow. Adaptive traffic signal control is an ATM solution for reducing traffic congestion through intersection signal (traffic light) optimization using real-time data. The essential components of the control system are roadside traffic sensors, a central computer (control center), traffic-signal controllers at the intersections, and a fiber-optic or wireless communication system. In recent years, Los Angeles and New York City have made significant investments in upgrading their traffic signals to adaptive control. See also: Active traffic management; Data communications; Highway engineering; Optimal control theory; Optimization; Traffic-control systems; Ubiquitous transportation network sensors

Although asphalt (also known as bitumen) is a naturally occurring substance found in deposits within the earth, it is also a by-product of petroleum processing. Almost all the bitumen used for asphalt pavement and roofs comes from petroleum refining and consists of hydrocarbon compounds that remain at the upper end (600°C or 1100°F) of the vacuum-distillation process. Because asphalt cannot be vacuum distilled, it has long been assumed that installed asphalt pavement and roofs do not emit hydrocarbon pollutants. Yet, according to a new report in the journal Science Advances (September 2020), asphalt pavements and roofs do, in fact, emit significant quantities of hydrocarbons, including polycyclic aromatic hydrocarbons (PAHs), particularly in environmental conditions found on hot and sunny days. This is problematic, because some PAHs are mutagens, teratogens, carcinogens, or endocrine disruptors and therefore harmful to human health and the environment. Hydrocarbons may also act as precursors to air pollutants, because hydrocarbons can react with nitrogen oxides (NO_x) and sunlight to form ozone, a major constituent of smog. See also: Air pollution; Aromatic hydrocarbon; Asphalt and asphaltite; Environmental toxicology; Nitrogen oxides; Ozone; Pavement; Petroleum; Petroleum processing and refining; Petroleum products; Roof construction; Smog

Although cats are the number one lethal threat to birds, collisions with building glass are not far behind. The number of birds killed each year by glass collisions worldwide is estimated to be in the billons. In the United States, the U.S. Fish & Wildlife Service estimates that between 400 million and one billion birds die each year from collisions with buildings. In contrast, an annual average of only 250,000 bird deaths result from collisions with land-based wind turbines. See also: Aves; Building; Glass; Wind power

Much of coastal and southern California has a Mediterranean climate, which is characterized by cooler, wetter winters and hotter, drier summers. Only drought-resistant plant species can survive without irrigation in this type of climate. Turf grass, for example, most certainly will not survive such dry summers without irrigation. And yet in 2015, four years into the latest California drought, some homeowners in southern California continue to grow turf grass and water their lawns. See also: Drought; Irrigation (agriculture); Lawn and turf grasses; Plant-water relations

Roman marine concrete, having lasted for nearly 2000 years, is a highly durable material. In contrast, modern marine concrete, which is made using Portland cement, may start to degrade in as few as 50 years. Researchers have now discovered why. As reported in the journal American Mineralogist (July 2017), they described the composition of the concrete and the chemical reactions responsible for its longevity. See also: Cement; Concrete

The Mississippi River has undergone extensive river engineering for flood control, with its 3500-mile Mississippi River and Tributaries levee (artificial-embankment) system. However, researchers reported in Nature (April 2018) that disconnecting the lower Mississippi from its floodplain has increased the flood hazard. The researchers determined this, in part, by analyzing floodplain sediments deposited for the past 500 years. They discovered that both the frequency and extent of flooding have increased in the past 150 years. During this period, land-use development in the floodplain and levee building also increased. The researchers concluded that while some flooding could be attributed to an increase in extreme weather events as well as to climate cycles, such as those of the El Niño–Southern Oscillation (ENSO) and the Atlantic Multidecadal Oscillation (AMO), most of the increase in flooding has been caused by river engineering. See also: River; River engineering

Naturally ventilating a house, such as by opening doors and windows, has long been considered an effective strategy for exhausting indoor air pollutants. However, according to researchers reporting in the journal Science Advances (February 2020), that assumption may be incorrect. The researchers observed that opening doors and windows reduced air-pollutant levels, but only temporarily. Within a few minutes after closing all doors and windows, pollutant levels returned to non-ventilated (original) levels. Why? As it turns out, indoor air pollutants are not just airborne, as are many outdoor air pollutants. Indoor air pollutants are attracted to solid surfaces to which the particles can easily attach, and from which they can subsequently detach. See also: Air pollution; Indoor air pollution; Ventilation