Struggling with a traffic control plan is just part of the job of being a general contractor. OSHA requires that every time the normal function of a roadway is suspended, temporary traffic control planning must be in place. But what do you really need to keep your work zone safe for your workers and the civilians? The seemingly numberless forms of signs, barricades, crash protection and so on make it difficult for anyone to muddle through the mess. And that’s not to mention the legal language! Unfortunately, this question is never going to have a cut and dry answer, but we can do our best to set you up with a simple little guide to get you started!
Making Your Traffic Control Plan (TCP)
The first step of any project that will disturb the natural flow of traffic is to write and approve your traffic control plan. This is the trickiest part of traffic control since it must be approved before you can push forward. If you’re not interested in trying to do it all on your own, there are traffic control contractors that will write the plan for you and get it approved. If you are looking to learn how to do it yourself, then continue onward! Every traffic control plan is made up quite simply of 4 different regions. There is the advance warning area, the transition area, activity area, and finally the termination area. Each zone’s function is completely different and as such, requires specialized traffic control equipment.
The Advance Warning Area
The advance warning area is just what it says it is. This is a stretch of road that is required to have varying forms of alerts available to the drivers to help them drive responsibly through the work zone. The distance the advance warning area needs to be depends on the conditions of the area in which you are working. If you are working in a way that doesn’t interfere with the traffic this entire section may not be necessary at all.
For an urban area the following conditions must be met:
- Distance must be greater than 200 ft
- To calculate sign spacing use this formula: (4 to 8)*MPH = Sign Spacing In Feet
For a rural area the following conditions must be met:
- Distance must be greater than 1,500 ft
- To calculate sign spacing use this formula: (8 to 12)*MPH=Sign Spacing In Feet
The Transition Area
The transition area of your traffic control plan is often treated as the most important area of the plan. In the transition area, traffic merges or deviates from its standard flow. The cones or barricades set up to guide the traffic together must cover a certain distance. Once again, this distance is entirely dependent on the road where the traffic is being diverged. The specifics for the taper for the transition area are quite complicated. So here we will give you a general rule of thumb, but we would highly recommend that you verify your work with the current MUTCD manual section 6C-3.
In the transition area there are 4 different kinds of tapers. A merging taper, shifting taper, shoulder taper, and a two way traffic taper. Each taper has its own purpose. As well as required dimensions. It’s important to note that unlike the Advanced Warning area, more distance is not always better. If transitions take too long, it can allow drivers to remain in the closed lane longer than necessary. Such behavior can drastically slow the flow of traffic through the work zone and create backups.
Merging Tapers
Merging tapers are the longest of all the tapers listed here. This is simply because it must provide enough room for two lanes of traffic to merge into one. As with the advanced warning area the distance of the merging taper is directly affected by the speed vehicles travel.
- For roads with speeds of 45 MPH and higher use W*S=Length Of Taper In Feet
- For roads with speeds lower than 45 MPH use (W*S2)/60=Length Of Taper In Feet
W is the lateral distance in feet of the shift in traffic. S is the speed in MPH.
Shifting Taper
A shifting taper is used when the vehicles will not be merging, simply shifting to pass by the construction zone. These tapers don’t require as much distance due to the lack of a merge. Once again the formulas differ depending on the speed of the road.
- For roads with speeds of 45 MPH and higher use (W*S)/2=Length Of Shifting Taper
- For roads with speeds lower than 45 MPH use [(W*S2)/60]/2=Length Of Shifting Taper
W is the lateral distance in feet of the shift in traffic. S is the speed in MPH.
Shoulder Taper
Shoulder tapers are a precaution on high speed roadways where road work is occurring on the shoulder. These roads often have shoulders that can be mistaken for another lane. The taper acts as a protective and alerting barrier that protects the workers and drivers. Because there is no merging happening or even a shift in the traffic these tapers can be incredibly short. As is standard. The calculation is dependent on the speed of the road.
- For roads with speeds of 45 MPH and higher use(W*S)/3=Length Of Shoulder Taper
- For roads with speeds lower than 45 MPH use [(W*S2)/60]/3=Length Of Shoulder Taper
W is the lateral distance in feet of the shift in traffic. S is the speed in MPH.
Two Way Traffic Taper
Two way traffic tapers are necessary when a two way road has been restricted to one lane. This kind of a taper often uses a flagger or a temporary traffic light to direct the opposing traffic through the open lane safely. This is the simplest of all the tapers to set up, with a maximum length of 100 feet and barrels placed every 20 feet.
The Activity Area
Up next comes the planning for the activity area. Not quite as complex as the transition area, but still fairly heavily regulated we would recommend that you double check your work with the MUTCD manual section 6C-2-C. This is the section where all work is occurring. The work space, traffic space, and the buffer space are the three sub-areas that make up the activity area.
The Work Space
The work space is the area where all workers, and equipment reside. The work space can remain stationary, or move as the work progresses. MUTCD standards do not regulate the size or dimensions of the work space. But the buffer space and traffic space often indirectly restrict the size of the work space .
The Traffic Space
The traffic space is the area where the traffic passes through the work zone. Once again there are no specific regulations regarding the size of the traffic space, but it must be at least wide enough for a vehicle to pass through.
The Buffer Space
Buffer space is an area that protects the crew and equipment from accidents that may occur in the traffic section. Nothing happens in the buffer space. It can’t be used as storage or for any activities. It must remain empty. There are 2 types of buffer space. The longitudinal buffer space, and the lateral buffer space.
Longitudinal Buffer Space
Longitudinal buffer space exists in between the end of the transition area and start of the work space. The MUTCD provides us with a simple chart we can follow to determine the size of longitudinal buffer space we need. The image below comes directly from MUTCD regarding the necessary lengths of longitudinal buffer space.
Lateral Buffer Space
Though lateral buffer space is important, it is up to the engineers in charge of the project to determine the width. There are no regulations regarding minimum width, likely because of the many instances when having lateral buffer space is simply not possible. To quote the MUTCD directly “The width of the lateral buffer space should be determined by engineering judgment”. However, if you can make the space we highly recommend it to keep your crew safe!
The Termination Area
Last but certainly not least comes the termination area. This area returns traffic back to it’s normal flow. Here the use of a downstream taper demonstrates to drivers that it is safe to return to the original path. If you do decide to set up a downstream taper they must be at least 100 feet long for every lane that was closed. Furthermore barrels need to be 20 feet apart in this section. If it is the end of the road work, then the use of an END ROAD WORK sign is totally acceptable. But, if another section of road work begins within the next mile those signs should not be used.
Detours, Diversions, One Lane Specifics, and much more
The information we have pulled out here provides a wonderful little guide for many of the simple applications for traffic control plans such as highway work. But there are a lot of other nuances and specificities when it comes to things such as one lane traffic control, curves, and detours. For guidance on keeping compliant with current standards we recommend that you always turn to the MUTCD manual and to a certified traffic control contractor. Their experience is a valuable asset when approving traffic control plans.