Road authorities regularly call for the provision of traffic impact studies (TIS) in order to assist in obtaining sufficient information to make decisions. The purpose of a TIS is to assess the effects of traffic caused by a proposed development and to identify improvements that may be required in order to ensure that the roadway system will operate at an acceptable level upon completion. Traffic impact studies concentrate on the evaluation of the operational impacts. However, one issue that is not generally explicitly addressed in a TIS is safety. Safety is an important element of the operation of a transportation system. The negative societal costs of motor vehicle collisions are staggering. Despite this, it is common to examine the impacts that will occur relating to traffic operations but not those relating to traffic safety. This does not have to be the case. Where development is proposed the undertaking of a safety impact study (SIS) is a new approach that can provide information to a road authority to allow them to assess the potential safety impacts that a development may have. This paper describes the development of safety impact study guidelines that have been completed for the Regions of Halton and Niagara in Ontario, Canada. The paper reports on methodologies by which the safety impacts of proposed developments can be assessed and offers commentary on how safety impact studies compliment traffic impact studies. It highlights how safety impact study guidelines are used to examine safety aspects of development submissions.