Roadside habitats have abiotic and biotic conditions that deviate from natural habitats and thus constitute “novel ecosystems” with insufficient adaptation of native biota. In roadsides, the net effect of positive and negative impacts determines population viability. This situation constitutes an “ecological trap,” when attractive habitats become demographic sinks due to locally reduced reproduction or increased mortality. The impact could be exacerbated by novel ecological factors. To investigate to what extent, for which species, and under which conditions ecological traps are actually occurring, we reviewed the effects of roadsides on plant and animal performance and population dynamics. We identified 390 relevant publications with 470 different effect cases based on a standardized literature review (2008–2018). Overall, 30% of these cases reported positive effects of roadsides on plant and animal populations, 31% of cases reported negative effects, and 39% showed no effects at all. In only 18 cases, negative effects were combined with positive ones, most often due to attractive but unsuitable habitats that constituted ecological traps. Ecological novelty was not used to interpret these effects. We conclude that there is abundant literature on ecological effects of roadsides, while specific research is needed on ecological traps, including potential effects of ecological novelty.