Highway Features

An intersection describes a situation where two or more roads cross at the same level. An interchange is a grade-separated intersection (one road passes over another) with ramps to connect them. Factors such as safety, cost, capacity, environment, development and politics can vary at every site; consequently there are hundreds of unique, one-of-a-kind interchanges worldwide. Interchanges are designed to fit specific local conditions and meet driver expectations.

Diamond Interchanges

When one road passes over another and there are ramps to connect them, that is considered an interchange. There are several types of interchanges, each offering different safety and convenience featur...

Roundabouts

A roundabout is a circular traffic intersection featuring yield control on all entering roadway legs, one-way continuous flow within the circulatory roadway, channelization of the approaching roadways...

J-Turns

The J-turn is an alternative to traditional roadway intersections on a four-lane highway. Instead of motorists crossing fast-moving lanes of traffic to get to the opposing lanes, drivers at a J-turn i...

ThrU Turns

ThrU Turns are a type of signalized intersection that helps improve traffic flow for individuals turning left.  The basic concept is that the vehicle drives through the intersection, makes a U-turn at...

Single-Point Interchanges

Single-point urban interchanges (SPUI) were first constructed in the early 1970s, and are used most often in tight right of way situations. Their primary feature is all four turning movements intersec...

Enhanced Pedestrian Crossings

MoDOT is using a new enhanced pedestrian crossing system at locations across the state. The new crossings make it easier for pedestrians to safely get across busy roads at locations that are not at si...

Continuous Flow Intersections

Continuous Flow Intersections (CFI) are a new style of intersection, developed in Mexico. In the U.S., CFIs have been implemented in Louisiana, Maryland, New York, and Utah. The first CFI in Missouri ...

Flashing Yellow Left-Turn Arrows

The Federal Highway Administration is now allowing departments of transportation to use flashing yellow left-turn arrows as an option on certain roadway intersections. In St. Louis, MoDOT has installe...

Guard Cable

The purpose of high-tension guard cable is to prevent vehicles that have left the intended travel portion of the roadway from sliding across the median and hitting oncoming traffic. Head-on collisions...