CONTACT:

First Last, Title

Office

Organization

000-123-4567 (phone)

000-123-4567 (fax)

firstlast@gov.us

First Last, Title

Office

Organization

000-123-4567 (phone)

000-123-4567 (fax)

firstlast@gov.us

Office of Office Title

Federal Highway

Administration

000-123-4567 (phone)

feedback@gov.gov

www.websiteaddress.html

Missouri Route 30 and Summit Drive, Fenton, MO 

DISPLACED LEFT TURN INTERSECTION 

THE PROBLEM 

A large commercial 

development called Gravois 

Bluffs opened across from a 

residential area. The existing 

intersection had a low level of 

service due to the increased 

traffic, which limited the area’s 

economic growth potential 

and hindered continued 

development on the corridor. 

THE SOLUTION 

The first Displaced Left Turn 

Intersection in Missouri was 

installed in 2007. 

THE OUTCOME 

Currently servicing up to 

50,000 vehicles a day, this 

intersection design proved 

to have several benefits, 

including: 

Mark Doctor, P.E.

N T FHWHA RE WesEoBur: ce Center 

404.895.6210 

O

mark.doctor@dot.gov

INTERSECTION LOCATION 

38°30’14.5”N 90°27’25.0”W 

• Improved level of service.

• Accommodating economic 

development. 

• Increased corridor capacity 

for future traffic volumes.

• Fewer and less severe 

crashes, most being 

property damage only. 

• Decreased cost when 

compared to separating 

the two roads with an 

interchange. 

CONTACT 

Jeffrey Shaw, P.E.

FHWA Office of Safety

202.738.7793 

jeffrey.shaw@dot.gov

FHWA-SA-14-056 Updated July 2020 

Background 

Missouri installed its first Displaced Left Turn (DLT), or Continuous Flow Intersection (CFI), in 

2007 in the city of Fenton in St. Louis County. Located near the major intersection of Route 

30 and Route 141, the intersection of Route 30 and Summit Drive needed to be rebuilt to 

accommodate increased residential traffic and growth in a nearby 

commercial area that was being 

developed.

“We were not getting the level of 

service we wanted, so we had a couple 

of people thinking outside the box ... 

[the DLT] turned out to be a great 

thing to help keep traffic moving”

.

Challenges 

Due to the expected level of growth 

at this intersection, Missouri DOT 

(MoDOT) required a new facility to 

accommodate not only current needs 

but also future growth. The agency considered the DLT as an option for maintaining an 

acceptable level of service and projected that if the number of vehicles continued to grow 

by 25 percent at this intersection over the next 20 years, the DLT will reduce vehicle delay 

from 2 minutes to just 30 seconds.1 

— Jeanne Olubogun, District Traffic Engineer, Missouri DOT

Approach 

MoDOT reviewed several options for addressing delay at this busy location, including innovative intersection designs. The DLT proved to be the only design capable of handling the 

projected increase in traffic while maintaining the existing level of service.

Results 

Partnering with the property owner of the nearby Gravois Bluffs commercial complex to 

finance construction, MoDOT was able to use the DLT as a way to maximize the main line 

green time while enabling left turns onto the side street to proceed at the same time,. This 

functional improvement increased

the green phase on MO 30 from 53 

percent to 64 percent.2 

In addition to this operational 

improvement, the DLT also proved 

to be a safe option. Once the facility 

had been constructed, there were 

very few crashes, and the ones that 

occurred were far less severe, with 

most being property damage only.

Left Turn Crossover at MO 13 and Summit Drive

Source: DLT Case Study Video FHWA-SA-14-055

1 Missouri DOT, “Continuous Flow Intersections” Web page. Available at: https://www.modot.org/continuous-flow-intersections

2 Engineering Design Source, Inc., “Welcome” Web page. Available at: http://engdesignsource.net/

www.safety.fhwa.dot.gov This Fact Sheet is a companion to the Video Case Study (FHWA-SA-14 -055)