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Traffic Engineering

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As more and more roundabouts are installed nationwide, people are becoming more acquainted with them as another form of intersection traffic control.  At appropriate locations, roundabouts provide an alternative to standard traffic signals or all-way stops that can provide a safer, more efficient, economically advantageous, and environmentally friendly way to move traffic along the roadway system.

Roundabouts can be safer than other forms of intersection control. At appropriate locations, roundabouts have been found to:

  • reduce conflict points;
  • promote slower vehicle speeds through intersections; and
  • reduce the number of injury crashes.

Slower vehicle speeds mean:

  • drivers have more time to judge and react to other cars or pedestrians;
  • an advantageous situation for older and novice drivers; and
  • a safer situation for pedestrians.

Roundabouts can be more efficient than other forms of intersection control.  At appropriate locations roundabouts can:

  • reduce delay,
  • improve traffic flow for intersections that handle a high number of left turns,
  • reduce the need for storage lanes, and
  • reduce fuel consumption and air pollution.

Roundabouts can be cost effective:

  • no signal equipment to install and repair;
  • savings estimated at about $5,000 per year in electricity and maintenance costs.

Flashing Yellow Arrow Signal


Several intersections in Longmont are equipped with the latest in traffic signal technology - the flashing yellow arrow. The flashing yellow arrow is part of a new signal display system that more clearly indicates to drivers when it is okay to make a left turn across traffic.

When making a left turn, drivers traditionally see a green ball, which means you can make a left turn, but must yield to oncoming traffic. Research shows many motorists are confused by the green ball and either fail to yield or think they are not allowed to make the left turn.

Federal Highway Administration (FHWA) research found motorists more clearly understood what to do when presented with the flashing yellow arrow. Further, the flashing yellow arrow provides more flexibility in signal timing operations as it can be optimized for certain times of day. This ultimately improves safety and improves traffic flow.

How the Signals Work
See the Flashing Arrow in Action!  View a brief video created by another community to demonstrate how these signals work. 



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