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Hello and welcome to the American Traffic Safety Services Association’s Work Zone Safety podcast series. This podcast is based on work supported by the Federal Highway Administration under the 2011 Work Zone Safety Grant. The purpose of this podcast is to discuss the hazards, safety considerations, and strategies associated with mobile work zone operations.
This podcast will begin with definitions related to mobile work zones and then discuss the elements and strategies necessary to maintain a safe mobile work zone operation.
This podcast will run for about 13 minutes.
So let’s talk about mobile work zone operations. The Manual on Uniform Traffic Control Devices, or the MUTCD, defines the mobile work zone as one that moves continuously or intermittently. An understanding of the differences between these two types of mobile work zone operations and the work zone traffic control measures associated with each will assist you with running the safest and most effective mobile operation possible.
Hey wait, I’ve heard different terms used, like mobile work zones, moving work zones, and intermittent work zones. What exactly are we talking about?
That’s a good point. Let’s start with a few definitions to make sure we’re on the same page.
As I just mentioned, the MUTCD identifies two kinds of mobile work zones: continuously moving and intermittent. Continuously moving work zones are mobile operations that generally move at a slow pace consistent with the pace of the work. Examples include pavement marking, rumble strip installation, and sweeping.
Work zones that stop intermittently are mobile operations where the work time at a given location is very brief and the work itself is usually repetitive in nature, with many stops along a section of roadway. Intermittent operations include activities like pothole patching, trash and debris removal, or other roadway repairs that require workers to make frequent short stops.
It’s important to remember that whether moving continuously or intermittently, a mobile work zone includes the same four components as a stationary work zone: the advance warning area, the transition area, the work area, and the termination area. Installing each of these elements is important for the safety of both workers and drivers and should not be overlooked. It is the nature of a continuously moving work zone that each component of the work zone travels forward at the same rate as the work being performed. For both continuous and intermittent operations, the traffic control devices used should be mobile–like portable changeable message signs, for example–and should be properly positioned at all times. Per the MUTCD, in cases where work will be moving at 3 mph or less, stationary traffic control devices such as signs may be used and should be moved ahead at intervals that maintain the minimum distances set forth in the MUTCD as the work progresses.
Okay, I’ve got the terms and definitions down. But what kinds of roadways would I use a mobile work zone operation on?
That’s an important point, too. Some conditions are going to be safer for mobile operations than others. For example, rural highways with low to moderate daytime traffic volumes and roadways with few intersections or interchanges are typically going to be more appropriate for this type of work zone. As you can probably imagine, mobile work zones on high-speed multi-lane urban roadways with frequent interchanges can be significantly more challenging, and a mobile work zone operation under these conditions may not be advisable due to the risk of accidents that can harm both workers and drivers.
I definitely want to avoid accidents and injuries. What are some ways I can improve safety in my mobile work zone operation?
Well, you can start by providing warning messages to drivers. While it is a good idea to issue advance information about planned mobile operations through public information channels like news programs and web sites, advance work zone warning to approaching traffic is a critical, required element to maintain during the operation. Mobile work zones rely on the use of highly visible devices and a well-organized approach that isn’t confusing to drivers. Devices like truck-mounted and trailed attenuators, portable changeable message signs, and arrow boards are very effective in warning drivers and protecting work crews. It’s also important to remember that the MUTCD requires all mobile operations, whether continuously or intermittently moving, to use high-intensity rotating, flashing, oscillating, or strobe lights to identify the work vehicles and warn drivers.
While the MUTCD does allow traditional stationary warning signs for operations moving at 3 miles per hour or less, it may be safer and more efficient to use only mobile devices, if they are available. State or local standards may provide guidance on which devices to use, but if it comes down to a matter of judgment, mobile devices are preferred. This is because it’s safer to deploy a work vehicle equipped with a message sign that can move ahead as the work progresses than it is to station signs on the roadside where they will need to be moved by workers, who are at increased risk of being struck by a passing vehicle.
Right, worker safety is a big concern. What kinds of things can I do to make my crews safer?
With the dynamic nature of mobile operations, a pre-activity safety plan and a meeting with the work crew is recommended to ensure that all crew members are briefed and aware of their roles. How the crew will communicate during the operation as well as contingency or emergency plans for responding to vehicle intrusion or other incidents should also be discussed and determined at this time.
In most intermittent work zone operations, construction workers will be present and on foot during the stops to perform their work activities, such as for pothole patching. Even though the stop time may be short, worker exposure to being struck by passing vehicles is still a major concern. Shadow vehicles with truck-mounted attenuators, or TMAs, effectively absorb impact and shield workers from being struck by errant vehicles that may intrude into the work area.
When using TMAs, an important safety factor to consider is roll-ahead distance. Determining safe distances between TMAs and workers on foot should take into account the distance that the TMA will roll ahead if struck by moving vehicles. Roll-ahead distances vary greatly depending on the size and speed of the vehicle that impacts it as well as the type of TMA you’re using. You should make every effort to maintain the minimum roll-ahead distance recommended by the TMA manufacturer.
Are there any other tips you can offer on how I can conduct the safest mobile work zone operation possible?
To improve the overall safety of any mobile work zone operation, consider including the presence of law enforcement officers in the operation. A law enforcement presence has been proven to gain the attention of drivers and deter speeding and aggressive driving. More alert drivers traveling at lower speeds improve the safety of both workers and motorists in the mobile work zone area.
Work zones in areas with narrow shoulders can cause lane encroachment, a sometimes unexpected and serious hazard because approaching traffic doesn’t expect the lane to narrow suddenly, which can result in collisions with equipment. This can be mitigated by advance warning signs that advise drivers that the lane ahead narrows due to the work zone condition and that they should slow down.
“Island” work zones can also be very hazardous and should be avoided. These are work zones that occur in the middle lanes of a multi-lane roadway, creating a moving “island” of activity. However, live traffic is moving on both sides of the mobile operation, causing very dangerous conditions. Some states, such as Washington, do not allow island work zones due to the heightened risk of intrusions and collisions with this type of operation. Rather than conducting a mobile work zone of this type, it is advisable to choose a safer option, such as conducting a stationary short duration operation in which either the left or right lane is closed, and to protect workers with TMAs or portable barriers, as appropriate.
Last but not least, the temporary traffic control plan is a useful and important tool and should be used to identify and develop mitigation strategies for specific hazards at the location where you are planning to conduct your mobile operation.
So, let’s summarize some of the key takeaways you should keep in mind.
- Communication–both among the work zone personnel and with the traveling public–is critical.
- Advance warning signs and devices are required. Portable changeable message signs are recommended and are very effective.
- Mobile signs (mounted to vehicles, for example) are preferred to having workers move standard ground-mounted signs from place to place manually.
- Shadow vehicles with TMAs and appropriate message signs are key devices for mobile operations, but it is very important to maintain adequate roll-ahead distances and use highly visible lead vehicles to maintain safety.
- Law enforcement presence can be an effective deterrent to aggressive or high-speed driving in the work zone.
- And finally, the Temporary Traffic Control Plan may be typical in nature but should also address the conditions and hazards that will be encountered and is the key tool for keeping the work crew on the “same page.”
The Work Zone Safety Grant Program has also supported the development of several related guidance products designed to help practitioners develop and deploy safe mobile work operations. These guidance products include:
- Maintenance Work Zone Safety Guide,
- Field Guide for the Use and Placement of Shadow Vehicles in Work Zones, and
- Temporary Traffic Control for Maintenance Operations.
To view these and all the guidelines and web-based training products developed under the Work Zone Safety Grant Program, or to find out about upcoming Grant-sponsored training courses, please visit the FHWA Grant page on the National Work Zone Safety Information Clearinghouse at workzonesafety.org.
This podcast has been a presentation of the Federal Highway Administration’s Work Zone Safety Grant Program. Thank you for joining us, and please visit workzonesafety.org often to view the latest training and guidance products.