Lives Saved by FHWA Roadway Safety Programs Forrest Council

Project Goals Initial goal – Examine changes in fatalities and crashes and estimate proportion of decrease related to FHWA programs (HSIP) Past studies indicate that major “causes” of crash/fatality change include not only safety programs, but also VMT and the economy.

What We Learned It’s not just MVMT and changes in the economy, but… It will be difficult to tease out effects of roadway treatment changes from vehicle changes from driver changes from economy changes…and New highly-rated NCHRP project will be awarded –“Identification of Factors Contributing to the Decline of Traffic Fatalities in the United States (2014-G-17)”, –Much more money and longer time than we have. So we changed methods…

Experiment Methodology Choose a couple of “popular” HSIP treatment types Find data on: –Miles/locations treated in US –Before-treatment (fatal) crash rate per mile or per location –Sound CMF giving percent decrease due to treatment Multiply together to estimate lives saved in US (…simple, huh?)

HSIP Data ( )

Treatments Chosen Trying to estimate lives saved due to –Installation of new traffic signal, and/or –Installation of left-turn lanes at signalized intersections –Shoulder rumble strips, and/or –Centerline rumble strips

Problems Encountered… Need estimate of miles/locations treated in US for each of these treatments. –HSIP does not have these data –Solution: a) Estimate percent, and thus amount, of total “intersection improvements” funds spent on new signal and left-turn lanes (and shoulder/centerline rumble strips) b) Estimate cost per installation and cost per mile c) Divide a) by b) to get number of intersections treated and number of miles of shoulder rumble strips installed –While HSIP has detailed data for some projects, over 85% of projects had to be classified as “other” due to lack of detail in the database. …

Problems Encountered (cont) So, where to find other data on… –Percent of total intersection treatments funds spent on left-turn lanes and new traffic signals? –Percent of total rumble strip treatments funds spent on shoulder or centerline rumble strips? –National cost per location and per mile for these four treatments? HSIS Safety Project History files for CA, NC and OH!

Using the Safety Project Files VHB extracted 2005 and later project data for intersection and rumble strip treatments from each State’s project file. Findings: –Many of the intersection treatment entries in the OH file are for “systems” (multiple locations), so not useful here. –No OH rumble strip entries after 2004 –At times, difficulties in determining type of treatment and whether single or multiple –Differences in categories used, spending patterns and in cost/treatment

Example Intersection Treatment Expenditures

Other Issues to be Resolved Find data on: –Previous slides – just estimates of miles/locations treated in US –Need before-treatment (fatal) crash rate per mile or per location No such national data exists Have some data from multi-state evaluation of shoulder and centerline rumble strips Still looking for before crash rates for intersections Will need to convert total crash rates to fatal rates using crash severity distributions –Need sound CMF giving percent decrease due to treatment Will have these!

Findings So Far As expected, lots of assumptions will be required to develop national estimates HSIS project history data is helpful, but does show differences between States –So re how to extrapolate differing NC and CA data to national average – no clue yet! “Simple” is never simple This is still an experimental effort…

Questions?