Moore-Ritchie, Chelsea

Minnesota does not currently have legislation enabling the use of speed safety cameras (SSCs), previously referred to as automated speed enforcement (ASE). However, due to an increase in speed-related fatal crashes on Minnesota roadways and research indicating the effectiveness of SSCs (TRS 2204), there is renewed interest in passing enabling legislation in the state. While the effectiveness of SSC programs has been widely agreed on, implementation of SSC programs is complex. This Transportation Research Synthesis was completed to better understand the complexity and best practices for SSC program administration and highlight considerations specific to Minnesota if enabling legislation were to be passed by the legislature. It also provides a summary of recent FHWA guidance documents, bi-annual reports from states with active SSC programs, and expert interviews conducted through the TRS process to better understand Minnesota specific considerations. Some of the topics covered in the report include: Citation Type/Processing Structure, Penalties, Equity Considerations, Commercial Drivers License (CDL) Implications, Top Concerns from Stakeholder Agencies, Public Perception and Revenue, and Funding.

Since the mid-1990s, the use of Speed Safety Cameras (SSCs), also referred to as Automated Speed Enforcement (ASE), as a speed reduction countermeasure has been growing across the US. Minnesota does not currently permit SSCs by law, but recent interest from community leaders has led to the reconsideration of the use of SSCs on Minnesota roadways. The purpose of this TRS is to review relevant research regarding the impact of SSCs as a standalone countermeasure to: reduce and manage speeds, to reduce the severity and frequency of crashes, and to understand spillover or other unintended consequences. Just over 150 communities and 20 states within the US are currently using SSC systems. Of the 13 methodologically sound SSC studies and four literature reviews that evaluated the effects of SSCs on driver speeds, all found some level of speed reductions for mean, threshold, and/or 85th percentile speeds. Of the eight SSC studies and six literature reviews that conducted multi-year crash history analysis before and after the implementation of SSC programs, all found reductions in the number of fatal and severe crashes. Of the studies that reported both overall crashes as well as serious and fatal crashes, all concluded that SSCs resulted in the greatest reductions for serious injury and fatal crashes. No increase in crash rates or other adverse safety effects were reported. Results are consistent with other literature reviews published from 2005 to 2010. The research indicates that SSCs are an effective countermeasure for reducing speeds, crash frequency and crash severity.

Minnesota statute provides for a wide range of school zone speed limits (SZSLs) from which local authorities may select. This Transportation Research Synthesis summarizes the current research regarding setting SZSLs, effective methods and procedures for setting school zone speed limits and known spillover or other unintended consequences for setting improper school zone speed limits to provide guidance on SZSL best practices. The majority of states use a statute to define a SZSL, with over half of these states having a statutory SZSL set at 15, 20 or 25 mph. Many allow jurisdictions to lower SZSLs further based on an engineering and traffic study. Minnesota statute allows for a larger range than any other state. Based on available research, SZSLs consistently reduce mean and 85th percentile speeds, however the extent of the reductions and statistical significance varies. In many cases, a SZSL resulted in lower compliance with speed limits, however, lower overall speeds and tightening and leftward shift of speed distributions indicate overall safety benefits. Crash histories through school zones overwhelmingly found reductions in crashes, in particular, reductions in fatal and serious injury crashes involving vulnerable roadway users. The speed differential between the approach speed limit and the SZSL has an impact on compliance and safety, with a recommended differential of 5 to 10 mph and speed buffer zones on high-speed roadways. The layering of additional countermeasures such as flashing beacons and geometric changes to the roadway are recommended as best practices to achieve lower speeds in school zones. No unintended consequences on vehicle speeds nor user safety were identified.