- Curves are supposed to be laid out so that curves/turns are marked as reverse curves/turns or winding roads if the distance between two or more alternating curves is less than 600'. Note that this rule usually requires some flexibility in mountainous conditions where a winding road has one or more curves that is sharper than others in a series of curves or turns.
- Curve warning signs with advisory speed signs are mandatory when a curve or turn is determined to require traffic to slow 10 MPH or more below the posted speed limit to safely maneuver
- Turn (W1-1) and Reverse Turn (W1-3) is supposed to be use when a curve has a posted advisory speed of 30 MPH or below. Exceptions usually are noted on roads with already low speed limits such as roads posted 40 MPH or below.
- Advisory speeds are also required to be determined using a ball bank reading, design speed equation (usually determined when a new road is being designed) or combination of ball bank meter and accelerometer. The results of the advisory speed study determine if a curve should be signed and the type of curve sign to use (curve/reverse curve or turn/reverse turn). The technology to determine advisory speeds has improved making this work easier and faster than in the past, but it is not being done consistently
- Chevrons (W1-8) must be spaced evenly based on the advisory speed posted from beginning to end of the curve (a table describing the required distance between signs was added in the most recent MUTCD). For instance, a curve with an advisory speed of 35 MPH requires 120' spacing.
- Chevrons may be posted only on the outside of a curve or turn.
- Two chevrons must be in view in all times when mounted in a curve or turn from beginning to end of the condition.
- Either chevrons or large arrow signs (W1-6) are mandatory on all curves and turns that have an advisory speed of 15 MPH or more below the posted speed limit.
- A licensed civil engineer is required to either oversee or conduct studies to determine locations of all curve warning, chevron and arrow signs (in addition to other signs).
- Improper Usage:
- Reverse curve/turn and winding road signs installed when distance between two or more curves or turns well exceeds 600'
- Curve or turn instead of reverse curve or reverse turn used when distance between curves is under 600' (sometimes on each curve)
- Use of W1-2 curve instead of W1-1 turn for a 90 degree or acute angle turn when speed limit is above 30 MPH presenting a special hazard to motorists who may not notice the lower advisory speed due to suggestion the curve is less sharp than it is.
- Lack/Excess of Curve Signs:
- Curve warning signs are not posted at all when a curve requires slowing to 10 MPH less than the posted speed limit
- Curve warning signs are posted when a curve is too gentle to require any signing and/or speed reduction.
- Inconsistent application is not uncommon: especially when knockdowns are not replaced
- Lack of documentation of curve sign locations meaning signs are forgotten about
- Improper Advisory Speed Study:
- Advisory speeds are frequently "determined" using methods that are based on nothing more than field observation by non-engineers or untrained technicians.
- This involves basically just driving the curve and getting a "feel" for the curve.
- These non-technical measurements are likely to lead to incorrect advisory speeds creating a hazardous situation for motorists, because one employee might "feel" that a very slow speed is a safe speed for a curve while another "feels" that a much higher speed is safe.
- The variation in field observation based on "feel" will lead to drivers ignoring underposted advisory speeds while excessively high advisory speeds can cause a vehicle to leave the road.
- Incorrect Posting of Chevrons/Arrows:
- Chevrons are often posted in a manner not conducive to MUTCD standards such as posting them in the fashion of arrow signs, posting only one in a curve or turn or posting them in clusters on only one part of the curve.
- Chevrons used where object markers or diamonds are required
- W1-6 arrows used improperly in the fashion of chevrons
- Lack of Supplemental Required Chevrons/Arrows
- Many, many curves and turns with advisory speeds 15 MPH or more below the posted speed limit lack any chevrons or arrows
- No prior speed reduction with W3-5 and R2-1 to adjust speed limit in hazardous curve area so that chevrons/arrows are not required when advisory speed is otherwise 15 MPH or more below the typical speed of the roadway
- Lack of Staffing on a Local Level for Curve Sign Studies
- Most local agencies lack the resources to hire, even as a consultant, a licensed traffic engineer just to conduct traffic sign studies.
- While the state may assist in this matter in state or federal-aid projects, there is nobody on the local staff properly trained to identify and correct errors or conduct traffic studies.
- States will not provide traffic studies for the local governments without charging as much as a private consultant
- This is how these errors become common. Some states do have state-funded county engineers, but this is no guarantee that the county engineer is actually handling traffic control matters as evidenced by the prior post about Morgan County, AL.
- Data and Documentation:
- Extensive documentation must be kept of sign plans with a dedicated replacement program to identify and replace worn out signs, stolen signs and knockdowns [records kept by transportation agency]
- A GPS database is needed showing sign locations, identifying their condition, age, location and MUTCD sign ID's
- Traffic Studies:
- Every public road, not just state roads, are supposed to have a traffic study conducted by a licensed traffic engineer with a traffic engineer thus overseeing work after sign projects are completed to make sure that signs remain consistent, none are missing and all meet MUTCD standards
- Few local agencies have this or can afford to have a dedicated traffic operations unit headed by a PTOE to make sure this is done
- Engineering Errors:
- Care must be taken to correct engineering mistakes such as signs placed in the wrong location, the wrong sign used or signs that were not identified in traffic studies (e.g curve posted in only one direction)
- These errors typically require someone with special knowledge on how to identify these errors meaning either state traffic operations must have supervisory authority on local roads or a regionally-funded PTOE must be hired full time to oversee roadways otherwise maintained by multiple local agencies since a single local agency lacks the resources for this
- Attention to Accuracy and Detail:
- Signs should be replaced correctly so that a W1-4 reverse curve sign is replaced with just that and not a W1-3 reverse turn or W1-2 curve sign
- Speeds Must be Accurate and Safety-Based
- Advisory speeds must be set correctly based on proper engineering studies
- To avoid excessive use of signs on very winding roads, speed limits should be adjusted lower in areas where an unusually high amount of curve warning and chevron signs would be required otherwise
- Deferment of Traffic Control Supervision to a Larger Agency:
- A local agency that lacks a staff engineer or its own traffic operations unit should be able to defer that responsibility to the state DOT or partner with other cities/counties in the region for that purpose, but this rarely happens. Note that the MUTCD recommends the latter.
- The first calls for state contracting, which most states refuse to provide to local governments while the second calls for regional services which are not available in most states.
After the creation of this field, only civil engineers with the PTOE certification or licensed traffic control technicians will be permitted to do this work with nobody else permitted to plan, design or install traffic control devices. Obviously, the licensed traffic control technician (LTCT) will have some limitations in that they will not be permitted to design larger structures such as sign bridges or any other overhead structure, but otherwise they should be capable of handling those responsibilities on condition that they are able to handle the math requirements. The license means that like an engineer they would be personally liable for not following proper engineering protocol. Breaking off this work from civil engineers placing the responsibility on a licensed non-engineer would make sense as a way of lowering the cost and raising the output thus raising standards. By doing this it would be possible for traffic control operations to be overseen by someone whose entire position involves collecting data, analyzing data, creating sign plans and then using a GIS database to store the records of that work with a legal requirement that is as binding as it is for the PTOE. A licensed traffic control technician would work under direct or indirect supervision of a PTOE and would typically still require a civil engineer to review all work plans. If working for a local government without an engineer on staff, the LTCT would be under supervision of the state's district engineer.
Overall, the extremely high amount of situations where this work is non-existent or incorrect shows how difficult this is to manage and is a major reason why State and Local Road Reform believes that most local governments are not well suited to handle the engineering and maintenance of traffic signs independent of a state agency or regional government unit. One of those reasons is because local governments were largely laid out based on antiquated principles, especially county and township government. The layout of most counties, small towns and townships was not done with any consideration of the high costs and organizational structure needed to meet modern transportation demands. Modern transportation demands cannot be effectively met without high economies of scale, people who know what they are doing and the benefit of adequate tax bases: both usually well above what the typical county or municipality can provide.
Further in this post a plan will be described that details how roadway classifications, traffic volumes and overall functions should be added to the MUTCD as a means of correcting extremes in curve warning sign policy ranging from too many signs to not enough signs. Overall, the federal government needs to be a better steward of traffic sign policy on both a state and local level. While the federal government does not have an iron clad way of policing bad traffic sign engineering practice, they should begin to hold states liable for this work not only on the state's own road system but also the local road system. If the state has not developed an effective strategy to permanently correct traffic control deficiencies including curve warning signs on local roads bringing them in substantial uniformity with MUTCD standards, then this will need to change. While all signs need to be in substantial compliance, focus is badly needed on proper curve warning sign engineering. Since the public and many states do not recognize the importance and technical nuances involved in this type of work, the federal government needs to have more authority in this area.
The best way to do this is to define safety improvements as a substantial amount of federal-aid given to states. Currently the federal government has some limited funding for this program, but it may be necessary for the federal government to begin to primarily fund traffic control devices to assure that states and local governments are installing and maintaining these devices correctly. Funding would be distributed to states to be divided between the state and local governments for traffic control devices. This funding, however, will be based on ratios of state control. This means if a state has 10% under state control and 90% under local control, then the state must spend 90% on local roads and 10% on state roads. Using the ratio method assures that states do not feel pressured to transfer roads to local governments as a means of raising and distributing funding. The ratio simply changes with the level of state control. This also puts less pressure on states to finance traffic safety work entirely on their own.
However, this federal funding must come with a catch. The federal funding to be used on local roads may not be distributed directly to local governments. It must be handled exclusively by state agencies and engineered through either state forces or private engineering firms hired by the state. Signs used on local roads must be purchased through state-approved private vendors and meet state standards with the states becoming liable for not just installation but also maintenance of these signs on local roads as long as federal funding is provided for continued maintenance. While the entire duty for traffic signs will not fall on the state governments, this new responsibility will require that state governments require local governments to meet the same specifications on anything they install thus creating a mechanism that states police local governments or else they will be required to handle that responsibility for local governments. This federal funding clause will also force local governments to organize traffic control cooperatives with other counties and cities as a way to properly finance and supervise traffic control when today the federal government generally ignores local government actions. Either way, the funding should be at a level to assure that local governments who are incapable of providing technical services on their own are provided a means to pool resources to either the state or regional level. States that fail to properly manage this federally-funded work for local governments and follow MUTCD standards will also risk losing all federal funding unless conditions are met to acceptable federal guidelines.
On federally-maintained roads and roads in the District of Columbia, a slightly different approach should be taken where one of three things occurs:
- DC contracts traffic control with an adjoining state or neighboring local jurisdictions to form a larger regional body that includes parts of adjoining states.
- Authority for traffic control shifts to the US Army Corps of Engineers
- Authority shifts to another federal agency that can oversee this work in a manner similar to a state government.
- A Contracting Approach
- States select individual roads annually in every county (or entire counties) for a review. They hire a private engineering firm to study these individual roads, including both state and local roads, to determine where there are missing signs (also including intersection warning signs) and to identify that hazardous curves and turns that require speed reduction
- The state will either provide funding to the local agencies to install the signs according to the study or provide the results expecting the local government to fund the install based on the review within a 2 year span
- This involves the frequently discussed approach of using state forces or special regional cooperatives to provide this service on behalf of the local governments so that all errors and emissions can gradually be identified and corrected
- The consolidation approach includes routine maintenance while the contracting approach requires periodic projects and updating of prior work to occur at least once every 10-15 years
Either approach will require sweeping reforms, and the cost of upgrades will be costly. The consolidation approach will not increase costs, but for conditions to improve in a shorter time frame additional funding will be required. The contracting approach, however, will require a significant annual investment from both state and federal funding. Using these findings this means that at the very least many existing curve warning signs will need to be:
- Modified if information is correct, but is displayed in a non-standard way
- e.g. R2-1 used instead of W13-1
- curve used where reverse curve is needed
- modify existing W1-2 and or W1-4 to W1-10 signs for intersections found in curves
- 24" curve signs used
- curve posted in one direction, but not the other
- chevrons/arrows are needed in curve
- sign locations are identified in studies, but none in the field
With no clear rules on the best approach based on traffic volumes, roadway characteristics and speeds, to a local agency it appears that every winding road and sharp corner needs curve warning signs when the budget for that work is simply not there. The result is that local governments typically either neglect the issue or take a very half-hearted approach. These are the questions a local government often might ask themselves:
- Should we install more signs than they can afford to maintain or do they take a modest approach and leave most roads void of any curve warning signs?
- Should we install and maintain signs well below MUTCD standards because having anything there is better than nothing at all?
- We are a mountainous area, so should we post any curve warning signs at all?
- We don't have the money for traffic studies, so should we just randomly post winding road signs on mountainous roads?
- Should we only post a curve sign where a previous accident occurred?
- Should we spend a million to fix every sign when there is no way we can afford to maintain that many signs?
This is how most rural roads in many states ended up with few to no curve warning signs at all while curve warning signs issued through state-aid roadway projects during the 1960's and 70's ultimately were left to rot by those same local governments within those same states states. This is especially true in those cases where small, low population local agencies were in charge.
- Incorrect curve sign used (e.g. posting W1-2 curve signs with no advisory speed for sharp 90 degree turns where a W1-1 is required)
- No advisory speeds posted on any curve signs
- R2-1 speed limit signs used to indicate advisory speed where W13-1 signs are supposed to be used
- No identification nor replacement of missing curve signs
- Incorrect advance placement distances (sign too close or far from condition)
- Non-compliant devices (e.g. incorrect design or dimensions)
- Improper use of signs (e.g. "Dangerous Curve Ahead")
- Incorrect chevron placement (e.g. chevrons do not follow through on curve, chevrons are on wrong side of the road or only one chevron is posted in a curve)
This curve on Edgemont Road north of Mong Road in Washington County, MD has incorrect chevron placement. Note that while "two are in view" they do not follow through from beginning to end of curve. Note the two chevrons in the opposite direction. (Photo from Google Street View, September 2012).
- No chevrons or arrows posted at all in a curve that requires a speed reduction of 15 MPH or greater from the posted speed limit
- Signs are dirty, old or not mounted correctly
These unnecessary signs create a greater liability to whatever agency is in charge of that road. Setting the speed limit to reflect conditions would be a far less costly strategy or simply adopting a "drive at your own risk" strategy posting a sign like "No Curve Warning Signs" with a plaque reading "Next X Miles". Inversely, this does not justify setting speed limits artificially low just to avoid posting curve signs. Speed limits should be set based on either roadway characteristics (majority of curves cannot be safety driven over 35 MPH) or prevailing travel speed. This means posting an arrow straight two mile long rural road at 25 MPH just because of a single 90 degree turn halfway through is not the intent of this policy. Likewise, residential streets, unpaved roads and low speed roads do not need the same investment in curve warning devices that roads with higher speeds require.
Creating an environment where more qualified employees exist to address traffic control needs would be helpful to improve curve warning signs as well as traffic signs everywhere. The current model of restricting this work to licensed civil engineers is clearly not effective given that most agencies cannot afford the cost required to hire a full-time engineer or engineering firm to do this work nor are the available engineers able to budget adequate time to this type of work. A licensed traffic control technician could help to focus efforts on an employee whose primary task is to handle traffic control work requiring a lower cost to hire than a civil engineer. This would help to bring more employees into the field with the knowledge and expertise to properly recognize, design, correct and install traffic control devices.
- Traffic Operations Cooperative Plan
- This engineer-driven approach creates the ideal conditions for unifying standards and creating uniform policy by removing primary responsibility for traffic control from the local agencies and transferring it to regional cooperatives or the state DOT
- Two-Way Consolidated Road Maintenance Plan
- This plan creates conditions where local control of traffic control is limited only to local agencies with the population and resources to adopt this strategy with additional heavy state-aid funds while entrusting the state DOT or regional cooperatives to handle all of the other roads across the state
- Local Exchange Plan
- This plan frees up resources available on the state level to gradually chip away at traffic control deficiencies by allowing the state to transfer resources typically used for labor-intensive maintenance work to technical work thus allowing the state to make incremental changes based on state DOT policy, which would likely include this new curve sign policy
However, state agencies can only do so much. The only way to assure a uniform and effective strategy to correct the currently ineffective curve warning sign methods is to create a more detailed nationwide policy that better explains to states and local agencies how to prioritize the installation and maintenance of warning signs. They can, of course, exceed these standards but this approach provides the best balance for resources between urban and rural areas while preventing roads that are sparsely traveled from being oversigned.