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The Jefferson County Transportation and Engineering Division maintains traffic control devices, regulates traffic, and studies traffic flow to ensure safety and efficiency. The Manual on Uniform Traffic Control Devices (MUTCD) is followed to determine appropriate use of traffic devices. These guidelines require certain criteria be met before a device can be used, and to ensure that motorists have consistency between communities throughout the United States.
Contractors build traffic signals in Jefferson County as part of capital improvement and safety projects, or larger private developments. All traffic signals on the Jefferson County roadway system are owned and operated by the county once constructed. Please refer to the Signalized Intersection List (PDF), for all traffic signals owned and maintained by the county.
Traffic signals located along state highways, (e.g. SH-93, SH-58 and at on-and-off ramps to C-470), are maintained by the Colorado Department of Transportation (CDOT).
Traffic signals located within incorporated cities or towns (e.g. Arvada, Lakewood, Golden, etc.) are maintained and timed by the respective local jurisdiction.
The Transportation and Engineering Division maintains traffic signals on unincorporated county roads. Signal maintenance staff is augmented at times with on-call contractors.
Pre-timed and traffic-actuated signals are the two types used on today's roads. Pre-timed controllers operate on a regularly-repeated sequence of signals and are used where traffic volume is stable and predicable. Traffic-actuated controllers change in response to traffic demand and are generally used where traffic volume fluctuates widely, and where interruptions to major street flow must be minimized. Jefferson County only uses traffic-actuated controllers for its signals.
The school zone beacons on roads within unincorporated Jefferson County are maintained by the Transportation and Engineering Division. They are set to turn on for the schools' start and release times (including kindergarten - midday). Traffic staff confirm start and release times through Jefferson County Public Schools on an annual basis.
Please report malfunctions to Transportation and Engineering at 303-271-8495 or [email protected].
Traffic engineers are required by state law to compare each situation to national standards that have been established by studying intersections throughout the United States. The Manual on Uniform Traffic Control Devices (MUTCD) contains criteria known as "warrants". Generally, warranted traffic signals control traffic flow effectively. Those that are not warranted may become additional hazards and other solutions to a traffic problem should be investigated.
Traffic signals can benefit the community and increase safety when used properly. However, traffic signals do not always prevent accidents or help control traffic. While traffic signals generally reduce the number of right angle collisions, the number of rear-end accidents may increase.
Jefferson County uses two diverse types of cameras at signalized intersections: intersection detection and closed circuit television cameras.
Intersection Detection Cameras - These cameras use video technology to detect when a vehicle is approaching a signalized intersection and are typically mounted on each approach to a signalized intersection. They are susceptible to false calls when heavy shadows, glare and snow occur. Please report malfunctioning traffic signals to Transportation and Engineering at 303-271-8495.
Closed Circuit Television (CCTV) Cameras - These are used by traffic staff to monitor traffic patterns and check on traffic signal trouble calls received, prior to traveling to the location. These cameras are actively watched by staff during peak travel periods or when an accident occurs. The cameras can be viewed on staff monitors. The county does not store footage from the cameras.
The majority of Jefferson County traffic signals are coordinated (timed), depending on the time of day, the location, and (when applicable) the primary direction of travel. To maintain consistent coordination of our traffic signals, time clocks at each intersection must remain synchronized, usually through the county’s central communication system. Coordinating traffic signals to facilitate traffic flow in both directions simultaneously (for example, when there is no clear primary direction of travel) is much more complicated than simply facilitating traffic flow in only one direction (e.g. a one-way street). There are many factors that can affect the design of timing plans, including: volume of traffic on the side streets, crossing time required for pedestrians, distance between traffic signals, speed limit on the main street, total overall traffic volume, volumes of turning vehicles, and number of lanes available for each movement of traffic.
Most of Jefferson County’s traffic signals operate on three different timing plans, which include weekday AM Peak, PM Peak, and Off-Peak plans. There are also special plans for weekends. There are a few timing plans in some locations for exceptional circumstances, like school traffic, weekend, heavy lunchtime traffic, or holiday shopping traffic. When traffic signals are not running in coordination, they operate in one of several different possible modes that depend on the equipment available at each intersection.
Additional factors, over which Traffic personnel have no control, affecting the actual effectiveness of the timing plans include: the actual speed of traffic, the acceleration patterns of motorists, variations in the volume of traffic during the timing plan, the frequency of emergency vehicle pre-emption, and the frequency of pedestrians (having pushed the button to cross) each cycle.
Progression of traffic on streets with coordinated traffic signals is typically designed to move traffic that came straight through the previous signalized intersection. If you turned onto the street from a side street, you may need to stop one or more times before you can get into the flow of traffic.
At some locations, it is necessary to accommodate turning vehicles due to the volume of traffic. Those are evaluated on a case-by-case basis. Generally, this only occurs at major intersections.
Yes, that type of operation is referred to as “Free Operation”. This type of operation is actuated, demand-responsive, and provides a “snappy” operation because it reduces the amount of time a vehicle must wait for a green light when there is no conflicting traffic present. The decision to run a signal in free operation usually involves several factors including: distance to adjacent traffic signals, volume of traffic, availability of video detection and other conditions like the presence of unique traffic generators (e.g. schools, large church, etc.) on the side street.
Traditionally, green arrows for left turning traffic appear before the through traffic gets a green light. To minimize delay at coordinated signalized intersections, it is sometimes necessary to bring up one or both left turn green lights after the conflicting through traffic has received a red light. This type of left turn operation is called a “lagging” left turn and is done under certain conditions for several reasons. The underlying reason, nevertheless, remains that at certain times of the day traffic engineers can get more cars through a signalized corridor that runs in coordination if they have the flexibility of lagging the left turns.
Jefferson County traffic signals are optimized for main street flow and the “Walk” signal that motorists see while driving on a main street is crucial for coordination. This tactic is referred to as (WRM) “Walk Rest Modifier” and does not affect wait times for side street timings. Another benefit is that bicyclists do not have to stop and push pedestrian buttons for a “Walk” symbol while riding on main streets.
When a pedestrian pushes the button on the signal pole, a pulse is sent from the button to the computer that controls the traffic signal (the “controller”). The controller will see this request for a “Walk” indication. At the appropriate time, a “Walk” indication will be provided. The button is like a light switch—after it has been pushed once, it is on until the “Walk” indication appears.
The standard time the “Walk” symbol (white-colored man) displays is five seconds. When the “Walk” indication appears, pedestrians may begin to cross if safe to do so. Once the initial “Walk” time has passed, the flashing “Don’t Walk” symbol (orange-colored hand) will appear. This means pedestrians that have not started to cross the road should stay on the curb. Pedestrians that are already in the road should finish crossing. The average pedestrian will have enough time to cross the entire road safely.
The flashing “Don’t Walk” time is based on the width of each roadway and the average walking speed of a pedestrian based on national standards. Once the flashing “Don’t Walk” time has passed, a solid “Don’t Walk” light will appear. This means that no pedestrians should remain in the intersection, as conflicting traffic has, or is about to receive, a green light. Most intersections are also equipped with “countdown” pedestrian indications, which display for pedestrians the exact number of seconds remaining before the pedestrian needs to be clear of the intersection.
There are several reasons why drivers and / or pedestrians wait for green lights or “Walk” signals. However, if the wait time is more than 120 seconds, there may be a problem with the traffic signal. If this occurs, please contact the Jefferson County Transportation and Engineering Division.
See Signal Intersection List (PDF) to determine if the county is responsible for the traffic signal.
Emergency vehicles associated with the fire districts are equipped with a special strobe light that, when activated, gives them the ability to change the traffic signals to green for the direction that the emergency vehicle is traveling. Law enforcement vehicles and private ambulance companies usually do not have this ability.
Traffic signals are equipped with conflict monitors that are designed specifically to detect equipment errors and prevent this from happening. If the conflict monitor detects a potential conflict, it puts the entire intersection into flashing operation. The intersection will remain in flash operation until a technician can fix the problem.
Occasionally, accidents or strong winds rotate signal heads (that display red, yellow and green indications) so they are visible to the wrong direction of traffic. This needs immediate attention.
Please report damaged or rotated traffic signal equipment to the Jefferson County Transportation and Engineering Division at 303-271-8495 or email [email protected].
Typically, the traffic signal will go dark. Some existing traffic signals have a battery back-up system (Uninterruptible Power Supply - UPS) that can maintain either normal or flash operation of the traffic signal. The UPS can maintain power for only a few hours and it is still crucial to remember that if traffic signals are dark, Colorado State Law (Colorado Revised Statute §42-4-612 or Colorado Model Traffic Code §612) dictates that motorists shall treat the intersection as all-way stop control, unless an officer is directing traffic.
(New traffic signals that have not yet been activated will have bags covering signal indications, so they are not confused with signals that have lost power. Motorists should continue to use the visible traffic control devices (like stop signs) if present.
Yes, please contact us at 303-271-8495 and we would be happy to arrange a tour of our facilities for individuals or small groups (e.g. Homeowners' Association boards, scout troops, school classes, etc.). Transportation and Engineering staff will show you how traffic signals work using the test bench in our traffic signal shop. We typically have a working traffic signal controller to demonstrate.
A flashing yellow arrow means left turns are permitted, but you must first yield to oncoming traffic and pedestrians and then proceed with caution. The flashing yellow arrow does not replace the solid yellow arrow and its meaning. However, it does replace the green "ball" indication as a signal for a yielding left turn.
*Light intervals are set short for this illustration only. Actual light intervals vary between signals, depending on traffic and the time of day.
The Federal Highway Administration allows communities to use flashing yellow left-turn signals on certain roadway intersections. Currently, Jefferson County has installed a flashing yellow arrow signal at the Bowles & Grant Ranch, Pierce & Chatfield intersections. The use of flashing yellow arrows are approved in the Manual on Uniform Traffic Control Devices.