How to Create a Safe Work Zone Using Maintenance of Traffic
Balancing the need to keep workers safe and keep traffic flowing isn't always easy, but it can be done.
Working in an area that is close to live traffic is extremely dangerous. Even though drivers encounter road construction zones daily, they can still make mistakes and careless choices. With people being distracted, impaired, rushed, angry, or aggressive behind the wheel, injuries and fatalities continue to happen (for related reading, see Distraction, Fatigue, and Impairment: What Any Safety Professional Can Do).
It is essential, then, that any work being done on or near a road, including construction, repair, resurfacing, and even landscaping, have a clear and thorough traffic maintenance plan.
What's Involved in a Traffic Maintenance Plan?
A traffic maintenance plan must ensure the safety of workers while also considering the drivers, pedestrians, cyclists, and persons with disabilities. The plan must also take establishing factors into account, such as the duration and timing of the work (day vs. night), the location of the work (on the road or on the shoulder), and road and traffic conditions. It should then consider the services and guides that will be required, specifically law enforcement assistance, flaggers and sign crew, signage, and cones and drums.
For crews working in a road lane, the activity area must allow workers to safely operate their equipment, including swinging machinery like excavators and cranes. There must be adequate space for traffic to pass, with a clear barrier separating live traffic from the road crew. This is usually achieved by deploying cones, but in some circumstances, especially for long-term projects, the assistance of local police or moveable concrete barriers will be needed.
Four-Part Traffic Maintenance Zone
In general, a safe work zone uses a four-part traffic maintenance structure.
1. The Advance Warning Area
The advance warning area uses signs to inform motorists of the type of work ahead and the distance required to merge into one lane. Warnings should start well ahead to give traffic the time and opportunity to merge, as well as offset the need for fast braking. Detours, alternate route signage, and timing signs (approximating how many minutes of wait time) should be posted.
The advance warning area is the starting point for cone deployment from the shoulder to the edge of the road (called a shoulder taper). This is essential since some drivers may use the shoulder for emergency driving. The construction zone must start at the very edge of the driveable surface of a road.
Arrow panels, directional lighting systems, or flaggers may be required in his area.
2. The Transition Area
The transition area uses cones to form a “merging taper” that advances across a lane to force traffic into the remaining live lane. It should also clearly establish the lateral buffer area to ensure sufficient space between the traffic and the workers on either side of the cone barrier. Planners should consider allowing sufficient space for wide trucks and inexperienced drivers of large vehicles like RVs.
To calculate merging tapers, use the following formula:
- For posted road speed limits of 40 mph or under: L = WS2/60
- For posted road speed limits of 45 mph or over: L = WS
- L = taper length in feet
- W = width of lane or offset in feet
- S = posted speed, or off-peak 85th percentile speed in mph
3. The Activity Area
The activity area is the zone in which the construction work occurs.
The first part of the activity area should be a buffer area, providing a space of protection for workers and traffic. The second part is immediately adjacent downstream, and is the zone for workers, machinery, and storage.
4. The Termination Area
Finally, the termination area is the end zone of the construction, and should include a short 100’ taper of cones back to the shoulder to clearly indicate the official end of construction.
Some sites simply stop the cones without a taper. But as with all road safety, clear indication is a better practice.
(To learn more, see Work Zone Awareness.)
Entrances and Exits for Construction Trucks
Construction zones may also require entrance and exit gates for dump trucks and other vehicles. These may require breaks in the cone barrier and must be clearly marked as entrance or exit gates, including instructions to truck drivers to never stop immediately upon entering (in case another truck is following).
Flaggers and Alternating Direction Lanes
On smaller, single-lane roads like an east-west road with one lane for traffic in each direction, if the westbound lane is closed for construction, the eastbound lane will have to alternate between eastbound and westbound traffic. This will require flaggers at each end who can communicate by radio or line of sight to ensure their "SLOW" and "STOP" signs are coordinated. This will ensure a safe, smooth flow or unidirectional traffic.
General Safety Tips
To keep a work zone safe while maintaining traffic flow, workers should always ensure that their activity takes place within the work zone and never in the live traffic lane. Whenever possible, work should be done facing the oncoming traffic. Any vehicles that need to reverse while in the work zone must do so with visual and audible warning devices, and ideally with the assistance of a flagger.
Pay attention to visual dangers like work lights and dust. Both may affect the ability of oncoming drivers to see clearly. Watch also for road cones or drums that may have been moved or hit, which creates a hazard in live lanes.
Nighttime construction and rain always add to the danger of a work zone due to reduced visibility. Be prepared for these conditions and adjust your approach accordingly.
Appoint one individual per shift to take stock of accidents or near misses, for compliance and insurance purposes, but also to improve safety in the future.
Working near traffic is always risky. But by balancing the needs of the work crew and the drivers, you can reduce risks and help workers get through the day unharmed.
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