THEY NEED TO PUT A LIGHT HERE!

By Sean Cashen and Robert Pergolizzi

Let’s face it, everyone has come across a situation where they are confounded that a congested intersection does not have a traffic light to allow for safe crossing. Well, getting a traffic light installed, or simply getting a left-turn arrow added to an existing traffic light is not a straightforward process. There are multiple regulations that govern the warranting, design and installation of a traffic signal. What may seem like an obvious location for a new traffic light may not be, once the overall framework of the roadway system and intensity of the nearby development is considered.

Local access management regulations (typically county governments) will determine whether a particular intersection meets spacing standards. On state maintained roads the Florida Department of Transportation (FDOT) is the regulating authority on traffic signals, median openings and driveways. Ease of access is critical for retail establishments and restaurants, which rely on passing-by customer traffic accessing their site. Safety is a primary concern, and installation of a traffic signal for safety purposes may be warranted; however, too many traffic lights create excessive delays for motorists, often times frustrating them and having them wonder why they are stopped so frequently. Ever sat at a red light when there was NO traffic on the side street, wondering what was going on? There is a delicate balance between ease of access and overall performance of the roadway system, or level of service (LOS) it provides. FDOT and county governments try their best to find the happy medium. But how do you go about getting a new traffic light or modifying an existing light for better performance?

Typically step #1 is to contact the local public works department or the FDOT or a local engineering consultant. Depending upon the type of roadway, the agencies’ signals spacing standards require a ¼-mile or ½-mile distance between adjacent traffic signals. In some cases, they may be closer together if there is a special need. This requires a variance to the spacing standards, which may be approved by the local government or FDOT after review of traffic figures and special circumstances.

We are currently working on an office project where the existing access, especially the exiting traffic, was marginal. In this particular case, the vast majority of the exiting vehicles needed a way to travel east to access a major north-south arterial road, but the main roadway access to the site did not allow this movement.  Another alternative was to “cut through” local residential roads to access a frontage road—with a dangerous merging maneuver—to eventually access a light that allowed access to this north-south arterial road.  After meeting with Pinellas County and the FDOT, both agencies agreed to allow a light at our site, even though the roadway fronting our site did not meet the spacing requirements (our light was too close to the light at the arterial road).  In this case, the benefits outweighed the negatives, since our proposed light would allow the county and the FDOT to close this adjacent frontage road and eliminate this dangerous merging condition.  In this case it was a win-win situation.  The moral of this story: it never hurts to ask.

If you believe your intersection complies with the standards, the next step is to engage an engineering consultant to perform a Traffic Signal Warrant Analysis which will be required by the regulating agency. These studies are conducted in accordance with the Manual on Uniform Traffic Control Devices (MUTCD) and evaluate traffic volume (eight hours, four hours, peak hours), pedestrian volume, school crossing, accident history, proximity to other traffic signals, and general conditions at the intersection. These studies must be prepared by a professional engineer and submitted for review by the appropriate governmental agency. Their review will consist of determining whether the installation of a new traffic signal is appropriate or whether median modifications or other improvements could be made to increase safety without adding a light. They will also analyze the effect a new traffic light may have on traffic flow along the major roadway, the proper traffic signal phasing, and time of day operations (i.e., part-time operation of the light).

Upon review and approval of the study, the matter may be heard at a public hearing for final approval, or the agency may seek to design and install the traffic signal itself. Often, developers are requested to design and install traffic signals as a condition of approval for their developments. In this instance, the permitting must be done by the developer‘s engineering consultant in cooperation with the permitting agency maintaining the road.  The same holds true for median openings for left-turn lanes.   There is spacing criteria for these as well, dependent on the type of road.   In some cases, these median “cuts” are allowed and they may actually improve the traffic circulation and eliminate other dangerous traffic movements like U-turns. 

The traffic problem might initially seem to have an obvious solution, but often it warrants considering a number of varying factors. In many cases it is prudent to contact an engineering consultant who can advise clients of the potential for new traffic signals and possible median openings, preparing the necessary studies, and designing and permitting the traffic signals.

About the Authors
Sean P. Cashen, P.E., LEED AP, has almost 25 years of experience in the civil engineering and land development consulting industry in the Tampa Bay area.   He is a founding member and Principal at Gulf Coast Consulting, Inc. He is a Florida Registered Professional Engineer and also a LEED Accredited Professional.   He received his Bachelors degree in Civil Engineering from the University of Notre Dame in 1985.