Over the last four years, a programme for the Californian State Road Authority; CALTRANS has worked towards production of a Best Management Practice Guidelines Manual for sensitive (rare, declining and most ‘at risk’/impacted by roads) herpetofauna crossings. Work has included assessment of current built structures, engagement within ongoing CALTRANS projects at various stages of completion and some experimental work including testing of old and new techniques. Examination of literature located 52 previous studies were examined concerning passage and barrier systems built as road and development impact mitigation fro herpetofauna. These concerned 50 amphibian and 75 reptile species or sub-species. Of the 7 discrete species-groups, snakes, lizards and frogs were the most studied, each representing about 20-25% of taxa, with 13 studies reporting salamander & newt taxa, 8 for toads, 5 for turtles and 2 of tortoise studies. Categories of information assessed were; passage construction and use, passage environmental variables and barrier construction and use. Crossing structures fell into five categories, largely reflecting the width of passage over or under roads. Very few of the studies represented large overpasses and other bigger crossing types with almost all considering passages of under 3.0 metres span. Results suggest than in most cases road impact mitigation planning has not been set against a quantitative objective but mainly to try to reduce direct road mortality. Monitoring of passage use has been generally poor in detail and duration and inconclusive but some improvements have been seen. Some controlled experiments manipulating key variables are indicative in showing effect and trends, however studies often have small sample sizes and low confidence inferences. Several examples of past mitigation have barely been recorded in available publications but activities were identified from references to pre- and post- construction assessments. The BMP will describe impacts and recommend planning and placement approaches for passages and barriers. It will describe mitigation design of passages and barriers and consider construction maintenance and monitoring requirements good quality, sustainable approaches including retrofitting existing roads. Aspects of integration with existing programs and themes such as proactive landscape de-fragmentaion and invasive non-native species control will be addressed. The BMP guidelines are to be finalised for 2020 and illustrations are currently being prepared. Practitioners are being invited to submit photographic or other illustrative materials that may help to provide clear illustration to the manual. Lists of needs are available from the main author. The output will hopefully be of sufficient generic value to be of use in other US States and countries overseas where guidance may be scarce.