This study investigated whether highways acted as barriers to gene flow for pronghorn in northern Arizona. DNA samples from 132 pronghorn were analyzed using eight polymorphic microsatellite loci. Samples represented animals living on opposite sides of US Route 89 (US 89) and State Route 64 (SR 64). Two different modeling approaches indicated that both US 89 and SR 64, and to a lesser extent US Route 180 (US 180), acted as barriers to gene flow. The genetic structuring caused by highways, especially across US 89, is consistent with behavioral data that demonstrated pronghorn rarely cross this highway. This study found no evidence of inbreeding or reduced genetic variation in any of the populations examined, but those effects may take longer to appear. Based on these results, the researchers recommend future genetic monitoring of these populations or assessment of genetic variation across highways with larger traffic volumes or longer histories to determine whether the barrier effects documented here lead to loss of genetic diversity.

The Arizona transportation history project was conceived in anticipation of Arizona’s centennial, which will be celebrated in 2012. Following approval of the Arizona Centennial Plan in 2007, the Arizona Department of Transportation recognized that the centennial celebration would present an opportunity to inform Arizonans of the crucial role that transportation has played in the growth and development of the state.

The report consists of a historical narrative and a series of topical essays. The seven-chapter historical narrative is a history of Arizona’s highways that extends from the pre-Columbian era to the present. The 14 topical essays extend the scope of the history beyond the state’s highway system. They include overviews of the development of other transportation modes (railroads, aviation, and urban transit), a brief history of highway pavements, a lighthearted look at the motoring experience during the 1920s and 1930s, and an exploration of how changes in transportation infrastructure affected some Arizona communities. The topical essays also provide additional historical information on bridges, urban freeways, the Interstate system, ADOT and its predecessor agencies, and famous roads such as U.S. Route 66, U.S. Route 89, the Black Canyon Highway, and the Beeline Highway.

The report also includes a timeline of transportation-related developments. This chronology not only provides an accessible overview of Arizona’s transportation history; it also places that history in a larger context by including transportation-related developments from the rest of the nation and around the world. Finally, the report contains a guide to archives in Arizona that hold significant collections of historical photographs related to the state’s transportation history, a bibliography of published historical sources related to the history of highways in Arizona, and a discussion of how the historical narrative and topical essays could be used to produce publications and media that would be made available to the public.

As Arizona’s population continues to grow, so does the need for electricity. Retail sales of electricity in Arizona have increased along with the population, although sales per person have declined since peaking in 2007, a sign of decreased use and increased efficiency. As we progress in the twenty-first century, action must be taken to increase the sustainability of our energy resources by continuing to conserve and by shifting to the greater use of energy from renewable sources. In addition, we must work to mitigate climate change by reducing greenhouse gas emissions.

Both the effect of climate change on our future water supply and the size of the population that will need to share in that supply are uncertainties that water planners must consider when making decisions regarding our future. We have options, but we have to be sure that we use water efficiently to meet our urban, agricultural, and environmental needs. This Policy Points offers a clear, succinct overview of the status of Arizona’s water supply and what the current drought really means for water availability.

In a desert city such as Phoenix, summertime heat is a way of life, but how much does the built environment contribute to the intensity of the heat on a summer night? In urbanized Phoenix, nights don’t cool down as much as in the surrounding rural areas and on more and more summer nights, the official Phoenix temperature fails to drop below 90 degrees. Climate plays a huge role in the comfort and quality of life of residents, with numerous implications for tourism, energy demand, water use, and the vulnerability of low-income families.

During the mid-part of the last decade, when the population growth rate was at its highest, the Phoenix area experienced rapid development and urban sprawl. The result has been an intensification of the Urban Heat Island effect. In this edition of Decades, author Sally Wittlinger discusses this uncomfortable consequence of urbanization.

The objective of this study was to evaluate the effect of typical chemical winter maintenance practices on Arizona Department of Transportation pavements. A review of previous studies on the effect of deicing/anti‐icing chemicals did not yield definitive recommendations, especially for DIAICs typically used by ADOT. Researchers conducted a laboratory study evaluating the effects of magnesium chloride, potassium chloride, sodium chloride, and distilled water on eight different open‐graded rubber‐modified asphalt concrete mixes using the boiling test. All experimental factors were found to be statistically significant, and the researchers provide recommendations on which DIAICs should be used for different binder and aggregate types.