Engineering for Zero
Safety is the primary goal for the Utah Department of Transportation. Transportation engineers use design principles that have been proven to be safe and reliable. National standards are used for signs and traffic markings to provide consistency for the traveling public. However, engineers continue to look for new and innovative ways to make transportation safer and more effective.
A cable barrier is a type of roadside or median safety barrier. Its primary purpose is to prevent a vehicle from running off the road and striking another object. The barriers are made of heavy-duty cables strung along a row of posts that provide enough strength to capture misguided vehicles like a net and redirect them from opposing traffic. This type of barrier is more forgiving than traditional concrete barriers.
Cable barriers are not effective or appropriate for every roadway. Cable barriers require a certain amount of space between the edge of the roadway and the barrier.
Crash cushions are intended to reduce the damage to motorists, structures and vehicles resulting from a car crash. They may also be designed to redirect the vehicle away from hazardous situations, roadway machinery and workers.
Rumble strips are an effective countermeasure for preventing roadway departure. The noise and vibration when driving over a rumble strip alerts the driver that they have left the roadway.
There are two types of rumble strips:
- Centerline Rumble Strips – Primarily used to warn drivers whose vehicles are crossing centerlines.
- Shoulder Rumble Strips – Used to warn drivers that they have drifted from their lane.
Continuous Flow Intersections
The Continuous Flow Intersection (CFI) is an innovative approach to intersection design. Compared to a traditional intersection, it reduces the steps in the light cycle and places left turns along a safer path. UDOT opened the first CFI in Utah at 3500 South and Bangerter in 2007.
- Bangerter Highway at 7000 South
- 6200 South 4100 South
- 3100 South and on Redwood Road
- 5400 South and 6200 South
ThrU-Turn Intersections (TTI)
The ThrU-Turn Intersection (TTI) concept is based on an innovative intersection design successfully implemented in other states around the country (the most common nicknamed the Michigan U-turn). The concept reduces delay, improves safety and maintains access at congested intersections by eliminating left turns at the main intersection and re-routing them to the nearby U-turn locations. By reducing left turns, the number and severity of crashes are greatly reduced. Additionally, the TTI is more bike and pedestrian friendly.
- 12300 South and State Street
- 5400 South West of Bangerter
Diverging Diamond Interchanges (DDI)
A DDI, short for Diverging Diamond Interchange, is a French engineering concept in which the two directions of traffic are crossed to the opposite side to provide easier access on and off the freeway. This reduces the number of traffic signal phases needed to move motorists through the interchange to two, as opposed to the usual three or four. DDIs efficiently move high volumes of traffic without increasing the number of lanes in an interchange. DDIs have a smaller footprint than a typical interchange, which is more cost-efficient.
- Bangerter Highway @ SR-201, Salt Lake City
- SR-92 (Timpanogos Highway) @ I-15, Lehi
- Pioneer Crossing/Main Street @ I-15, American Fork
- 500 East @ I-15, American Fork
Flex lanes (also called reversible lanes) is a congestion management tool used to accommodate heavy rush hour traffic by alternating the direction of the lanes during peak hours of the day. The concept is an effective way to increase traffic flow when widening is not an option. Flex Lanes are most effectively used on roadways with traffic congestion primarily in one direction during peak travel times. Many corridors and freeways throughout the country successfully use Flex Lanes to reduce traffic congestion.
Flex Lane Location:
- 5400 South Redwood Road to Bangerter Highway
Flashing Yellow Light
The Department of Transportation (UDOT) and several jurisdictions throughout Utah are among the first in the United States to implement new flashing left turn arrows.
Traffic signs and pavement markings are strategically placed along the road to provide important regulatory, warning and guidance information to motorists and all other roadway users. Sign size, shape and colors are an important part of making each sign readily recognized by motorists, especially those traveling at high speeds.