Traffic Signal timing
Street Light Requests
How do I request a:
Deaf Child sign
Present a doctor's note to the Department of Transportation (4th floor of City Hall).
How do I get the speed limit changed on my street?
Transportation staff will investigate requests before the city traffic engineer can make a determination. Call (919) 560-4366, ext. 36415, or visit the Department of Transportation on the 4th floor of City Hall.
What does a flashing left-turn arrow mean?
A flashing yellow arrow means left-turns are permitted, but drivers must yield to oncoming traffic, pedestrians, and bicyclists. These new signal displays are designed to make it easier for drivers to know what to do when making a left-turn and reduce accidents at signalized intersections. The key for drivers to remember is what the signal colors mean — red means stop, yellow means use caution, and green means proceed.
For information, contact Larry McGlothlin at (919) 560-4366, ext. 36435 or by e-mail.
How do I get a traffic signal installed in my neighborhood
The Department of Transportation installs and maintains traffic signals within the city in accordance with the Manual on Uniform Traffic Control Devices (MUTCD). The MUTCD is approved by the federal highway administrator as the national standard for all traffic control devices. Traffic signals are installed based on an in-depth engineering study, as outlined in the MUTCD. The City’s director of transportation approves the installation of signals when traffic studies indicate a signal is warranted and beneficial. The North Carolina Department of Transportation (NCDOT) must also approve signal installation on state system streets.
The City Department of Transportation maintains more than 380 traffic signals citywide. A computerized traffic control system coordinates the timing at all signals. The computerized system in conjunction with signal coordination plans helps reduce travel time, number of stops, air pollution emissions, and also reduces fuel consumption. Identifying locations that warrant a traffic signal is an on-going initiative to insure the health, welfare, and safety of the motoring public. In addition, new development, changes in traffic patterns and citizen concerns may initiate a signal warrant study or update.
To request a new traffic signal, contact Larry McGlothlin by email or call (919) 560-4366, ext. 36435.
Traffic Signal Justification
An engineering study of traffic conditions, traffic volumes, pedestrian activity, intersection geometry, and the physical layout of the surrounding road grid network is first gathered. This data is then compared to national guidelines, or "signal warrants," for determining whether a traffic signal is justified. If one or more of the following eight signal warrants is met, a signal may be justified; however, satisfaction of one warrant in and of itself is not necessarily sufficient justification. Engineering judgment as to the site-specific characteristics shall dictate the need for a signal installation. Under no circumstances, should a traffic control signal be installed unless it enhances the overall intersection safety and/or operation.
1. Eight-Hour Vehicular Volume
The need for a traffic signal shall be considered if one of two conditions is satisfied. The first condition considers if a certain number of cars use the main street and the side street for eight hours within a 24-hour period. The number of cars needed varies based on the number of lanes. For example, if the main street and the side street each have two lanes, there have to be 600 vehicles an hour using the main and 200 an hour using the side street. The second condition considers the interruption of continuous traffic where the traffic volume on the major street is so heavy that traffic on a minor intersecting street suffers excessive delay.
2. Four-Hour Vehicular Volume
This warrant considers if there is heavy volume on both the main and side street for any four-hour period of a day. This is based on a sliding scale, where the more volume there is on the main street, the less volume is required on the side street to satisfy this condition. Other variables such as speed and number of travel lanes also factor into the curve.
3. Peak Hour
This warrant is intended for use at locations where traffic conditions are such that for a minimum of one hour out of the day, the minor-street traffic suffers undue delay when entering or crossing the major street. This is also based on a sliding scale where the volume relationship between the major and minor streets determines if this warrant is satisfied. Speed and number of lanes are variables that also factor into this equation.
4. Pedestrian Volume
The pedestrian volume is intended for applications where the traffic volume on a major street is so heavy that pedestrians are impeded from crossing the main street. Volume of 100 pedestrians an hour in any four hour period in the day or 190 pedestrians in a one hour period satisfies this requirement.
5. School Crossing
Consideration is given to installing a signal at locations where school children have to cross a major street. This warrant takes into consideration the number of gaps in traffic flow when children are crossing the roadway and where there are a minimum of 20 students during the highest crossing hour.
6. Coordinated Signal System
Sometimes progressive movement in a coordinated signal system can necessitate installing a signal where it may not otherwise be needed in order to maintain proper grouping of vehicles. This warrant is mainly based on the spacing of the adjacent traffic signals.
7. Crash Experience
This warrant is applicable where the frequency and severity of crashes are the principal reason for installing a signal. If trial alternatives and enforcement fails to reduce the crash frequency; then, five or more accidents, of types susceptible to correction by a signal, within a 12-month period and where the vehicles per hour are 80 percent of the volumes listed in the tables for warrant 1 satisfy this condition.
8. Roadway Network
Installing a traffic control signal at some intersections might be justified to encourage concentration and organization of traffic flow on a roadway network. This warrant considers various conditions associated with total entering volume from all approaches.
If you would like to request a new traffic signal, contact Larry McGlothlin by email or at (919) 560-4366, ext. 36435.
How do I request a stop sign for my neighborhood
Stop Signs and Four-Way Stops
The City of Durham Department of Transportation installs and maintains traffic control devices, including stop signs, in accordance with the Manual on Uniform Traffic Control Devices (MUTCD). The MUTCD is approved by the federal highway administrator as the national standard for all traffic control devices. Stop signs are installed based on an in-depth engineering study, as outlined in the MUTCD. The City’s Director of Transportation approves the installation of stop signs when warranted. The North Carolina Department of Transportation (NCDOT) must also approve stop sign installations on state system streets. The Transportation Department routinely conducts investigations as part of an ongoing Accident Reduction Program. In addition, citizen concerns may initiate an engineering warrants based study for stop sign installations.
To request a new stop sign, contact Larry McGlothlin by email or at (919) 560-4366, ext. 36435.
Stop Signs and Four-Way Stop Justification
Multi-way stop control can be useful as a safety measure at intersections if certain conditions exist. An engineering study of traffic conditions, pedestrians, bicyclists, and physical characteristics of the intersection is first gathered. This data is then compared to the national guidelines for "multi-way stop sign installations" for determining whether a four-way stop is justified. It is important to note that the intended use of a four-way stop is to enhance overall intersection safety and/or efficiency.
1. Interim Measure
Where a traffic signal is warranted, multi-way stop control is an interim measure that can be implemented quickly to control traffic until the signal is designed and installed.
2. Crash Experience
A crash problem is characterized as five or more reported accidents in a 12-month period that are susceptible to correction by multi-way stop control. Such crashes include right and left turn collisions as well as right-angle collisions.
3. Vehicular Volume
Total vehicular volume entering the intersection from all approaches must average 300 vehicles per hour for any eight hours of an average day and the combined vehicular, pedestrian, and bicycle volume from the minor street approaches must average at least 200 units per hour for the same eight hours, with an average delay to minor street vehicular traffic of at least 30 seconds per vehicle during the maximum hour. However, the minimum threshold is 70 percent of the values noted above when the 85th percentile speed of traffic approaching on the major street exceeds 40 mph.
4. Other Criteria Considered
a. The need to control left-turn conflicts
b. The need to control vehicle /pedestrian conflicts
c. Sight distance restrictions
d. Where equal approach volumes exist and would improve operation
Important to note: Multi-way stop control can be useful as a safety measure when used appropriately. Stop signs should not be viewed as a cure-all.
Many people believe that stop signs reduce speeding on residential streets, when in fact the opposite has been observed. Traffic and safety engineers note that drivers may actually increase their speeds between signs to compensate for the time they lost by stopping. Unnecessary or unwarranted stop sign placement is likely to result in noncompliance; thus, resulting in more crashes.
Another popular misconception is that stop signs act as a deterrent for cut-through residential traffic. Studies have not only revealed that speeds are affected for only 100 to 150 feet before and after stop sign placement, but traffic volume remains unchanged as well. In addition, too many stop signs can cause drivers to ignore the right-of-way rule or some drivers may simply choose to ignore the stop sign.
In summary, stop signs should not be used for speed or volume control.
If you would like to request a new traffic signal, contact Larry McGlothlin by email or at (919) 560-4366, ext. 36435.
Traffic and Safety Studies
In 2003, the City of Durham Department of Transportation began developing a procedural outline for instituting an Accident Reduction Program. This program identifies, implements, and monitors improvements to intersections with the intention of reducing fatalities, frequency of crashes, property damage, and injuries at intersections in the city.
This program strives to both treat existing dangerous intersections and proactively treat potential problems.
This new initiative has led to nearly 200 investigations. As a result of those investigations, 92 countermeasures have been implemented and 18 proposed countermeasures are pending due to funding, approval, or are in design.
Since inception, tracking data shows a 36 percent reduction in targeted crashes, 21 percent reduction in total intersection crashes, 27 percent reduction in injuries, and a 26 percent reduction in property damage. Durham’s effort to find and treat crashes has made a positive difference at locations treated with countermeasures. As these treatments are permanent the safety benefits will continue to accumulate into the future.
The Department of Transportation encourages the public to report safety problems. If you see a safety problem, contact Larry McGlothlin by email or at (919) 560-4366, ext. 36435.
Traffic and Safety Study Methodology
The City of Durham uses a combination of methods to identify study locations. Some common techniques used are the frequency method, accident rate method, severity method, statistical method, cost method, rate quality method, frequency-rate method, and hazard index method. Experts agree that there is not one method used that is superior. The City uses a systematic approach based on the frequency and severity methods to identify candidate study locations. However, as needed, other methods may be used as supplemental tools.
A comprehensive eight-year accident history is maintained for all intersections, with five or more recorded accidents. From the compilation a ranking, based on average crashes per year, is used to find problem locations. Simultaneously, an annual ranking of intersections based on severity is compiled. In combination, this can be an effective means to hone in on locations that have both a high frequency of accidents and the highest likelihood to result in severe injuries.
From here an in-depth engineering study is undertaken to determine the cause of the accidents. Possible countermeasures are selected based on a field investigation, collision diagrams, other transportation engineering studies, technical literature, and previous experience.
The selection of a countermeasure is crucial and typically is discussed by a group of engineering professionals internally, before a final decision is made. After a countermeasure is selected, the recommendation is forwarded to the governing agency. Upon approval the countermeasure is implemented. For evaluation purposes a "before condition" diagram is sealed on the date of implementation. An "after condition" diagram will be opened and maintained for a period equivalent to the time period used to identify the problem, typically three years. The "before" and "after" condition is evaluated on a regular basis to monitor the effectiveness of the improvements.
1. Common Probable Causes
Common probable causes include, but are not limited to the following: large turn volume, restricted sight distance, absence of a left-turn traffic signal phase, inadequate roadway lighting, improper pavement markings, inadequate advance warning signs, and inadequate signal timing.
2. Typical Accident Reduction Countermeasures
Typical countermeasures include, but are not limited to the following: warning signs, guide signs, regulatory signs, sign placement, delineators, pavement markings, traffic signals, signal visors, signal back plates, supplemental signal heads, modified signal timing, modified clearance intervals, phasing upgrades, signal flashers, and removal of sight obstructions.
We encourage the public to report safety problems. If you see a safety problem, contact Larry McGlothlin by email or at (919) 560-4366, ext. 36435.