The field of road ecology, slowly emerging over two decades, offers great promise to transportation, nature and society, and a recent book, Road Ecology: Science and Solutions, should help catalyze the field. The objective of this article is to provide additional insight into the book by highlighting its process of development, and pinpoint some underlying bases for expecting the field to accelerate. The book evolved from: recurrent environmental problems; early international work; and TRB and ICOET initiatives. Fourteen co-authors from academia and government, including two spearheaders, four transportation experts, one hydrologist, nine ecologists, and a supporting cast of forty from the transportation and environmental communities created the book. Several broad challenges required solutions: present the best possible science; reveal an array of useful applications; avoid drowning in detail; and mesh authors to complete the book in two years. Also key specific decisions molded the book: title, publisher, sponsors, and royalties; focus on USA, Canada, and mainstream road network; peer-reviewed literature, and no specific solutions recommended; several topics with minimal, and with ample, coverage; and the nature of the final chapter. Since publication, salutary evidence indicates that the book is reaching: the transportation and environmental communities; educated public and conservation organizations; and decision-makers. Several trends in addition to the book seem to be catalyzing the field of road ecology. Rapid growth in research and the development of useful applications is evident, and important promising opportunities now lie on the palette of the diverse specialists. The conceptual objective of the field for society appears to be safe and efficient mobility meshed with natural processes and biodiversity. Thus the area along and adjoining the entire road network should significantly improve ecologically, while also strengthening the network of ecological flows and large green areas across the land.

Pinpointing major objectives as a vision for transportation and society provides a cost-effective framework for numerous detailed solutions along the road network. Three major objectives, with road ecology a central player, are highlighted: (1) improve the natural environment close to the entire road network; (2) integrate roads with a sustainable emerald network across the landscape; and (3) integrate roads with near-natural water conditions across the land¬scape. These are briefly described along with examples of possible key steps ahead. In effect, this big picture or vision is a cost-effective route to achievement and benefit for transportation, the environment, and society.

Improving ecological conditions around the road network is emerging as a significant objective of transportation, along with providing safe and efficient mobility. Reading landscape patterns is a key to success. The prime goal of this article is to identify ecologically appropriate and inappropriate locations for road construction, removal, and mitigation in the network. Other goals include understanding the effect of road location between two large natural patches, and progress in developing an ecologically optimum network form. Simple spatial models are used with three independent variables: (1) road size or connection, (2) road location relative to natural patch or corridor, and (3) size/width of patch or corridor. Dependent variables are habitat loss, degradation, and fragmentation. Modeling results suggest that in a landscape of dispersed natural patches and corridors, by far the greatest road effect (ecological impact) results from a highway that bisects or highway network that subdivides a large natural patch. Overall, effects are greatest where a road crosses or is alongside large patches and wide corridors. For both types, the least effect is where a small road is alongside the margin. Road effects are relatively low around narrow corridors and lowest around small patches. Model results indicate that the probability of species crossing between two large natural patches is lowest where a highway slices across near the midpoint. A highway network has a greater effect on habitat conditions in a natural landscape than in an agricultural or suburban landscape. Habitat degradation appears to have a greater ecological effect than does habitat loss or fragmentation in the landscape. An ecologically optimum road network contains: a few large roadless areas; a few busy roads rather than many lightly used roads; and perforated roads (for species movement) between the large roadless areas. In conclusion, a simple patch-corridor analysis of a landscape points to clear solutions for locating road construction, removal, and mitigation to maximize ecological benefits. The two overarching principles are minimizing roads in and around large natural patches and maximizing effective habitat connectivity between the large natural patches.

An extensive area of frequently mowed open grassy roadsides is designed for highway safety, yet paradoxically, in many locations woody vegetation of various types may make safer highways, and additionally provide diverse valuable benefits for society. Therefore our objective is to identify the goals of greatly increasing woody vegetation, consider the pros and cons, and identify the especially desirable and undesirable locations for it. Today, frequent costly roadside mowing favors many non-native species including invasives. Rare species also live on roadsides, including nearly a quarter of the U.S. federally listed threatened-and-endangered plant species with at least one roadside population. The prime goals of greatly increasing woody roadside vegetation are to: (1) increase wildlife habitat, biodiversity, and landscape connectivity; (2) increase highway safety and driver experience; and (3) decrease pollut¬ant and peak-water-flow inputs to nearby water-bodies. The first goal has few disadvantages and also accomplishes diverse societal benefits. The second goal emerges from a modest decrease in vehicle speed in appropriate areas, plus the use of visually diverse types of roadside woody vegetation. An entrée into the travel-behavior and wildlife literature indicates that drivers drive more slowly on narrow than wide two-lane highways, and suggests that a sharp drop in wildlife/vehicle crashes appears between a posted speed limit of 90 and 70 km/hr (55 and 45 mph). The third goal enhances nearby streams, ponds, and other water bodies, mainly by significantly improving conditions in roadside ditches. Tall shrubs or natural forest/woodland are especially desirable vegetation types for >50% of the 35 situations common along road networks. Mowed grass is especially desirable on 17% of the situations, essentially the most risky driving locations. Meadow/low shrubs and small trees with herbaceous layer are intermediate in overall roadside value. We conclude that a massive increase in woody roadside vegetation offers numerous transportation, environmental, and societal benefits with minor disadvantages. Evaluation by a blue-ribbon panel of diverse experts and widespread pilot projects with research and monitoring are valuable next steps.