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Appropriate deceleration on approaches to roundabouts is primarily accomplished through the use of applicable geometric design principles; however; traffic control devices (specifically signing and markings on the approach) also serve a vital role in communicating to the approaching driver what speed profile should be anticipated. This report provides a resource for engineers to identify and select appropriate speed-reduction treatments for high-speed approaches to roundabouts. The research examines best practices and research literature on speed-reduction techniques for high-speed approaches for all intersection types; as well as treatments for work zones and horizontal curves. Based on the findings from these efforts; the report summarizes a selection of treatments including traditional signs with and without beacons; pavement markings; illumination; speed-activated signs; and transition zones. Information on the effectiveness of these treatments; as well as potential costs of installation and maintenance; is provided for the practitioner to determine which treatment(s) best suit the site under consideration. Guidance is also provided for the methodology of conducting a speed study to determine the speed characteristics of a site; as well as links to resources for additional information. The project identifies a number of research needs specific to particular treatments as well as the general need for field research of the recommended countermeasures specifically on approaches to high-speed rural roundabouts.

This toolbox is one of the deliverables for the culmination of several phases of a project, which evaluated driver behavior in work zones using the SHRP2 Naturalistic Driving Study (NDS) data. The toolbox summarizes information about work zone traffic control devices, countermeasures, and work zone features that have a demonstrated impact on speed in work zones. Features were identified through a survey of the literature. Additional information for some of the features and countermeasures was gained through the various analyses of SHRP2 data conducted through this project. Guidance from the work zone traffic control manuals for various states was summarized when appropriate. Recommendations for use of each feature or countermeasure relevant to addressing speed in work zones was developed by the team and reviewed by work zone experts and the project panel.

This report is one of the deliverables for the culmination of several phases of a project, which evaluated driver behavior in work zones using the SHRP2 Naturalistic Driving Study (NDS) data. This study utilized SHRP2 NDS to evaluate the impact of traffic control devices in reducing driver speed in work zones. The main advantage to the SHPR 2 NDS data is that on-road driver behavior was captured and can be used to evaluate how drivers behave in various situations. The study included four different analyses. The first evaluated where drivers began reacting to various work zone traffic control devices. The second assessed how drivers changed speed upstream to immediately downstream as they encountered various traffic control devices. The third assessed how drivers react when they encounter the back of a queue and the fourth developed speed based on work zone characteristics such as presence of barriers.