Improving Safety through Missouri’s Intersection 

Safety Implementation Plan (ISIP) 

Introduction 

The Federal Highway Administration (FHWA) provided technical assistance to Missouri in the winter of 

2008 to develop an Intersection Safety Implementation Plan (ISIP). FHWA held a workshop, provided a data 

package, and identified a list of candidate intersections by countermeasure 

type. Lastly, they provided the completed ISIP to the State in May 2009. Prior 

to the ISIP, the Missouri Department of Transportation (MoDOT) focused 

on improving intersections with high volumes, but the ISIP introduced 

MoDOT to applying a systemic approach. With this approach, MoDOT can 

install low-cost, effective countermeasures at a large number of locations with 

moderate to high crash frequencies. Missouri has also identified improving 

intersection safety as one of the top nine strategies in its latest Strategic 

Highway Safety Plan. 

Process and Results 

The development of the ISIP engaged key individuals and managers from all 

MoDOT districts, as well as its central office. Out of 1,108 stop-controlled 

intersections with crash histories identified in the ISIP, MoDOT began its 

implementation effort by successfully installing lowcost sign and pavement marking improvements at the 

top 250 intersections. This project was completed in 

2013 and 2014. 

Advance intersection warning 

sign. Source: MoDOT. 

Additionally, as a direct result of the ISIP, Missouri 

adopted new policies related to implementing signal 

enhancements through its existing signal maintenance 

cycle. These low-cost, systemic countermeasures 

include adding reflectorized backplates, adjusting 

clearance intervals to be in compliance with the ITE 

formula, and limiting or eliminating the use of latenight flashing operations. Traffic signals in Missouri 

predominantly use 12-inch LED lenses and have one 

signal head per lane; however, if any inconsistencies 

are identified as part of its maintenance cycle, 

MoDOT will give consideration to addressing the 

inconsistency as part of the maintenance operation. 

Low-cost sign enhancements at a stop-controlled 

intersection. Source: MoDOT.
 

 

 

Finally, Missouri used the ISIP to initiate corridor-level intersection 

improvements for portions of U.S. Route 54 and U.S. Route 30. The 

improvements involved both low-cost and higher-cost infrastructure, 

education, and enforcement activities along the corridors. The State 

reconfigured several two-way, stop-controlled intersections on atgrade expressways to incorporate J-turn treatments to address highspeed angle crashes. Although J-turn intersections are higher-cost 

improvements, they are proven to be very effective at improving 

intersection safety along high-speed divided highways with crash 

histories. The early success with J-turns has helped it gain traction; in 

2008, Missouri had only one J-turn intersection, but—by the end of 

2015—there were 19 J-turn intersections installed across the State. 

Expected Outcome 

J-Turn Intersection. 

Source: Tennessee DOT. 

To fully implement the ISIP, MoDOT would implement these treatments at 3,234 intersections, requiring an 

investment of approximately $50 million beyond currently-programmed intersection safety projects over the 

current 4-year period—or $12.5 million annually. MoDOT personnel and local municipalities implement 

some of the signing and pavement marking countermeasures when possible, thereby reducing the level of 

necessary funding. MoDOT has continued to initiate many intersection improvement projects and recently 

identified its high-need intersection locations. However, each district must prioritize its safety needs annually 

and include the projects in the district safety plans. MoDOT is pleased with its progress to date and intends 

to implement additional intersection countermeasures identified in its ISIP. 

Contact 

Jon Nelson 

Traffic Safety Engineer 

Missouri Department of Transportation 

573.751.1157 

Jonathan.Nelson@modot.mo.gov 

FHWA-SA-16-080 

Revised June 2020