The 2013 National Work Zone Awareness Week is nearly upon us. The week of April 15-19 is dedicated to the cause and the theme for this year is "Work Zone Safety: We're All In This Together"
PSA in a workzone.
The 2013 theme highlights the complexities of work zones, especially in urban areas, and the need for awareness and planning on the part of everyone affected by work zones – DOTs, road workers, drivers, bicyclists, motorcycles, pedestrians, emergency response, law enforcement, utility workers.
In 2010, work zone crashes killed 576 people and injured an estimated 37,000. As you can imagine, road work is a dangerous occupation; in fact, 10 to 15 percent of work zone fatalities are workers. But, surprisingly, that also means that 85 to 90 percent of those killed in work zone crashes are drivers and their passengers.
Thankfully, work zone crashes are preventable.
One way OTW Safety has worked to reduce work zone crash fatalities is through the development of Longitudinal Channelizing Devices, or LCD's. Longitudinal channelizing devices (LCDs), previously referred to as longitudinal channelizing barricades (LCBs), were first introduced in the 2003 Manual on Uniform Traffic Control Devices (MUTCD).
Per the current version of the MUTCD, LCDs are described as lightweight, deformable devices that can be connected together to delineate or channelize vehicles or pedestrians.
[caption id="attachment_2650" align="alignleft" width="550"] LCD in use, Parley's Canyon, Utah.[/caption]
LCD’s are much safer in use than temporary concrete barrier, which, when impacted by a wayward motorists, create high G forces that can cause serious injury and death to the driver and occupants of the vehicle.
Unfortunately, LCDs have only been used to delineate pedestrian travel paths in work zones. As such, LCDs have ensured that the temporary pedestrian travel path meets the MUTCD accessibility requirements for persons with disabilities.
Although LCD’s are exceptional at meeting this requirement, there are other uses where LCD’s are accepted by the FHWA, but are rarely considered. For instance, LCD’s can be used in place of concrete barriers to close roadways to vehicular traffic. Closing roads using concrete barrier exposes motorists to extremely hazardous high angle impacts. Using LCD’s to close roadways instead of concrete barrier mitigates this hazard.
[caption id="attachment_2653" align="alignleft" width="550"] Road Closure with Concrete Barrier I-15 Salt Lake City[/caption]
LCDs can be used to denote the edge of the pavement or separate the active travel lanes from the work area, where positive protection is not required. Again, using LCD’s in this manner greatly reduces the risk to motorists and their passengers of an impact with concrete barrier.
In contrast to traditional channelizing devices(e.g., cones, drums, etc.) that have some open space between devices, LCDs can be connected together to form a solid line. Thus LCDs can prevent drivers and pedestrians from going between devices and entering the work area (whether inadvertent or deliberate).
A solid line of LCDs also provides continuous delineation of the travel path, which may be beneficial at major decision points in work zones, such as lane closures, exit ramps, business access points (i.e., driveways) and temporary diversions (i.e., crossovers).
[caption id="attachment_2658" align="alignleft" width="550"] This vehicle is pulling into the wprk zone from a side alley and is headed into oncoming traffic.[/caption]
LCDs also are considered to be highly visible and have good target value, thus LCDs might increase the sight distance to the lane closure. In addition, the larger size of the LCDs may allow for increased spacing of the devices (i.e., more than one times the speed limit in mph); thus fewer devices would be needed.
LCDs connected together reduce the potential for missing devices. In addition, ballasted LCDs are more resistant to becoming misaligned by passing vehicles and / or weather.
The current mindset set of the safety community is geared toward using “positive protection” to protect maintenance workers in roadway work zones. As a result, concrete barrier has become the temporary traffic control device most commonly used in roadway work zones, even when the data from work zone accident fatalities overwhelmingly indicate that maintenance workers are in the minority of those killed in work zone. In fact, a recent ATSSA sponsored survey of practices confirmed that temporary concrete barrier is the option most frequently used by state transportation agencies. This has occurred even though the data from work zone accident fatalities overwhelmingly indicate that maintenance workers are in the minority of those killed in work zone.
Traffic engineers expect concrete barrier to improve safety for the motorists and reasonably protect workers, but motorists can be subject to average forces of 9.55 G's and as high as 23.5 G's when impacting at 25 degree angles when traveling in standard size pickups. The same vehicle when impacting water-filled LCD’s at 25 degrees measured average ride-down accelerations of 5.05 G’s with the highest measurement at 7.4 G’s. Keep in mind these angles are low and motorists can expect much higher forces when striking barriers that have been located perpendicular to traffic flow to close lanes.
[caption id="attachment_2660" align="alignleft" width="214"] Results of 25 Degree Impact at 100 KPH[/caption]
It is clear, when the crash test data is reviewed, that plastic water-filled longitudinal channelizing devices create more positive outcomes in the event of an accident than the use of traditional concrete barrier due to the high G’s that motorists are subjected to when impacting concrete barrier.
If 85% of work zone accidents fatalities are drivers and their passengers, and water-filled longitudinal channelizing devices provide a higher degree of safety for the motorists passing through work zones, it would seem logical that water-filled longitudinal channelizing devices would be the traffic control device of
choice. But these devices are rarely if ever used. In road construction work zones, resistance to change to use of water-filled longitudinal channelizing devices (as with many devices new to the transportation infrastructure environment) slows industry-wide adoption of water ballast devices.
There is an enduring familiarity with concrete and a tendency to rely on concrete barrier for every use, even when it is not the safest or most appropriate device for the job. Because there is no requirement or incentive for change, engineers simply continue to specify temporary concrete barrier for all traffic control jobs, in spite of the innovation of safer and more effective mechanisms.
Temporary concrete barriers are appropriate in work zones when needed for positive protection, but can create hazards in themselves if used simply for channelization.
For decades, road transportation departments, consulting engineers, and others who specify safety equipment in roadway construction projects have had few choices in traffic control devices. Historically, engineers have specified temporary concrete barriers as a “one solution fits all” solution, and a culture has developed leaving temporary concrete barrier as the default option for channelizing delineation. In order to reduce the number of work zone fatalities, these transportation professionals are urged to examine and consider new products offering vehicle occupants a safer environment. When practitioners begin to look beyond familiar traffic control products, work zone safety will be improved. The occupants of vehicles traveling through work zones are frequently exposed to temporary concrete barrier being utilized as a delineator or to close a road, elevating exposure to high angle impacts. Or, alternatively, they are required to drive through a confusing array of delineators, risking head-on collision.
Those vehicle drivers and occupants could be your family or mine, so we must ask ourselves if we are really considering all of the available traffic control devices and how the proper deployment of these devices can create safe work zones, preventing injuries and perhaps saving lives. Surely, it is worth consideration in this week of workzone safety.
February 20, 2013
by OTW Safety filed under