Transportation is the backbone of developing regional economies and the evolution of our civilization. Well planned road systems are essential to connect dispersed communities or cities. However, roads are one of the major destructive forces to regional ecosystems and the natural environment. The effects of roads on their adjacent ecosystems may include road kills, habitat fragmentation, barrier effect to animal movement, road edge effects, introduction of exotic species, pollution and noise, change of micro-climate, etc. This study undertakes a comprehensive survey of road kills in Kinmen (Taiwan) and analyzes their causes. The road crossing behaviors of animals have been utilized in deriving survival probability by employing Traffic Flow Theory. Two models, Traffic Flow Model and Linear Model, have been proposed in this study and comparisons of survey results and the models are also carried out. Comparing the survey results and predictions of models, both models yield similar results for moderate traffic flow and provide excellent agreement in predicting frequency of road kill of birds and small mammals. It is found that traffic volume, adjacent landscape and road condition are the major factors in road kills. Higher traffic volume near animals’ habitats always augments the probability of road kill, however roadside trees, adjacent landscapes, and road longitudinal slope may also affect the probability of successful crossing by small animals, especially birds. The barrier effect of roadside trees forces birds to fly between tree trunks and enter onto a collision course with oncoming vehicles, so that dense roadside trees may lead to higher bird casualties. On the other hand, roads with abrupt turns or steep longitudinal slopes may block the view of small animals and may be a significant factor in increasing the probability of being run over by vehicles. Based upon the findings of this study, some mitigation measures to lower road kill probability are

The ecological system and natural resources of small islands are limited. Especially, their ecological system is very vulnerable to the invasion by alien species. The planning of development in small islands must be very delicate and advanced comparing with large islands or continental areas because there is no tolerance for experiments or mistakes in developing small islands. This research is aimed to obtain the acceptable road density for small islands from the ecological point of view and taking Kinmen Islands (Taiwan) as an example. Three derivations of finding the acceptable road density for small islands were developed in this analysis. One method is to adopt the allowable density of roads for sustaining viable populations of wolves in continental areas to small islands. Since wolves are the top predators of a healthy ecological system and with sustainable wolf population the ecological system is believed to be sound, this road density could be the ideal one for a small island. However, the allowable road density for wolves was obtained in continental areas and it is not clear that if it is valid in direct application on small islands. The second method is modifying the road density from model islands to fit the ecological characteristics of objective islands. In this research I took Okinawa (Japan) as the model island and derived a suitable density of roads for Kinmen. In the third method, I selected the largest small island as the model island and applied the derivation procedure of the second method to find another ecologically ideal density of roads for Kinmen. The result has shown that the smaller islands have higher density of species but should have lower ideal road density. It was also found that the current road density of Kinmen has exceeded the results obtained by the three models. Although this research is focused on Kinmen, it is believed by the author that the same approaches could be applied to other small islands when reviewing their road-developing policies. The applications of this analysis on habitat islands or ecologically isolated zones in continent areas have been demonstrated. It has been shown that the procedures and results of the application are similar to those for small islands. Key words: road density, small islands, ecological impacts, Kinmen. (The full text of this paper can be found in Ecological Engineering, 2006.)