As departments of transportation face the challenges of repairing and improving their roadway pavements and bridges, one obvious point is clear.
Most roadwork is performed in traffic conditions
Most of the repairs and bridge-deck replacements will be performed under traffic conditions. The days of building new roads in open fields without existing traffic has been replaced by improving existing facilities while maintaining traffic and providing for the safety of workers and motorists during the repair process.
The basis for designing temporary traffic control begins with the information shown in Part 6 of the Manual on Uniform Traffic Control Devices (MUTCD). Part 6 provides the minimum traffic-control requirements needed to establish safe work zones for construction, maintenance, utility, permit and emergency operations. State DOTs are allowed to enhance the minimum requirements shown in the MUTCD; however, they cannot develop less-stringent requirements. Virginia is one such state that has enhanced the minimum requirements, having written its own version of Part 6 titled the Virginia Work Area Protection (VWAPM) manual. The first VWAPM was issued in Virginia on Jan. 1, 1984, and it has been steadily improved commensurate with each revised edition of the MUTCD.
There are various reasons why we have enhanced the minimum standards, including the desire to increase the visibility of temporary traffic-control devices, enhance the advanced warning messages and improve the channelization of motorists, increase safety for workers, and make the installation of temporary traffic-control devices easier to perform. This has been achieved by using larger, brighter and additional devices installed with spacing more reduced than that required in Part 6 for such devices.
One area we improved upon is the advanced notification of lane closures via signage.
For a typical right-lane closure on a freeway, the MUTCD calls for a “ROAD WORK (XX) MILES; RIGHT LANE CLOSED (XX) MILES and a RIGHT LANE ENDS symbol sign.” The recommended spacing of these signs is “1⁄2 mile between the first and second sign, 1,500 ft between the second and third sign, and 1,000 ft between the third sign and beginning of the lane closure” for a total distance of 5,140 ft from the first sign to the lane closure.
Workers are required to wear ANSI Class 3 garments.
In Virginia, the signage for this same lane closure would begin with a ROAD WORK AHEAD sign, followed by a RIGHT LANE CLOSED AHEAD sign. Next would be a LANE ENDS MERGE LEFT sign on the right side of the roadway and a KEEP LEFT sign across from it, followed by the RIGHT LANE ENDS symbol sign. The recommended spacing range between these signs is 1,300-1,500 ft, allowing for adjustments to be made in the field due to ramps or geometric conditions. The total distance between the first and last sign ranges between 5,210-6,000 ft, with the most informative of these signs, the RIGHT LANE CLOSED AHEAD sign, at a distance of 3,900-4,500 ft from the lane closure, allowing more time for motorists to understand what’s going on and which lane they need to move out of before the lane closure decision point. In addition, installing the signs at equal spacing allows motorists to see the next sign in the series as soon as they pass the previous sign, building upon their expectation that they are approaching a work zone, as opposed to traveling half a mile between the first and second sign as per the MUTCD guidance.
Our specifications require the use of 48-in. by 48-in. retroreflective warning signs for all lane closures, regardless of the roadway type or time of day. For increased visibility and recognition of these signs, we require all temporary warning signs to be fluorescent orange prismatic lens sheeting signs. For flagging operations on two-lane roadways, we’ve included a BE PREPARED TO STOP sign in addition to the MUTCD required ROAD WORK AHEAD, ONE LANE ROAD AHEAD, and FLAGGER symbol sign, again with equal spacing of the signs, allowing for greater reaction time by motorists.
On all interstate and limited access highway lane closures, the VWAPM requires a minimum lane closure taper length of 1,000 ft, regardless of the posted or actual speed of motorists, allowing for easier merging of traffic. The MUTCD “requires lengths ranging from 660 ft for 55-mph highways to 840 ft for 70-mph highways.” In Virginia, during nighttime conditions all merging tapers on these same highways require the use of 36-in.-tall drums with 6-in.-wide stripes of prismatic lens sheeting for greater visibility and better delineation.
For channelization of traffic the MUTCD “allows 18-in.-tall cones to be used during daytime and [on] low-speed roadways, and a minimum cone height of 28 in. on freeways and other high-speed highways.” The VWAPM requirement is for the use of 36-in.-tall cones on all roadways regardless of type. One reason for this change was a review of statewide work-zone crash statistics revealing that more crashes were occurring on lower speed and volume roadways, where smaller devices were allowed to be used. To improve the consistency of our work zones, VDOT requires all devices to be the same size and type for channelization, reducing the error of a work crew arriving on a jobsite with the wrong size or type of device for the roadway they need to work on.
The spacing of channelizing devices as per the MUTCD “should not exceed a distance in feet equal to 1.0 times the speed limit in mph when used for taper channelization, and a distance in feet equal to 2.0 times the speed limit in mph when used for tangent channelization.” Knowing that most work crews don’t carry a measuring wheel with them, and to make it easier, quicker and safer to install channelizing devices, we simplified the placement of devices into divisions of 40-ft spacing found in pavement markings (10-ft broken line, 30-ft gap between broken lines) to the following: For posted speed limits of 35 mph or less, 20-ft spacing between devices in tapers and 40-ft spacing in tangent sections; for posted speeds greater than 35 mph, 40-ft spacing in tapers and 80 ft in tangent sections. Another VWAPM requirement is for the use of drums in unmanned work zones to ensure that the channelizing devices don’t blow over when no one is on the jobsite to maintain them.
The MUTCD allows the use of various sizes of arrow boards, “ranging from a 48-in. by 24-in. Type A board for low-speed roadways up to a 96-in. by 48-in. Type C board for high-speed roadways.” In nearly all of our Typical Traffic Control figures, we require the use of a Type C arrow board, which provides a minimum legibility distance of 1 mile, allowing greater reaction time by motorists. When placed on shoulders, we require the placement of a four-drum taper to delineate both arrow boards and portable changeable message signs, as well as the placement of conspicuity markings along the trailer frame of these devices.
The MUTCD shows the use of a shadow vehicle in some of their typical application figures, which provide protection to workers as they perform their activities on the highway. In a few instances, the use of a truck-mounted attenuator (TMA) device is shown on the shadow vehicle as an “option” on most roadways or as a guidance condition on high-speed highways. The VWAPM shows the use of a shadow vehicle for all lane and shoulder closures, and since July 1990 has required the use of a TMA on the shadow vehicle as a standard condition for the following situations: When closing a lane on a four-or-more-lane roadway with a posted speed of 45 mph or greater; when working on ramps and loops of interstate and limited-access highways; when a mobile operation occupies all or part of the travel lane on a multilane roadway with a posted speed of 45 mph or greater; or other locations as determined by the regional traffic engineer. It is not uncommon to have several TMA crashes per year in work zones established by state forces, as well as several more in work zones set up by contractors. In nearly every crash, the injuries were minor compared to the consequences if the crash cushion was not installed on the back of the shadow vehicle. One other condition we place on the use of TMA shadow vehicles is that during the operation as a shadow vehicle with a TMA, the truck shall not be used as a work operations vehicle. All material and/or equipment on the shadow vehicle TMA shall be properly secured to prevent spillage if struck by an errant vehicle.
To assist with guidance through long-term work zones, the VWAPM requires the use of 8-in.-wide temporary pavement markings and raised pavement markers placed every 20 ft in lane-closure tapers and lane shifts. To better delineate barrier service used in long-term work zones, 8-in.-wide by 12-in.-tall fluorescent orange prismatic lens sheeting barrier panels are installed on top of the barrier spaced on 80-ft centers along the tangent sections and 40-ft centers along the taper sections. Barrier delineators are required along the traffic side of the barrier in-between and at the same spacing as the barrier panels approximately 24 in. up from the roadway surface. In addition, a Type B flashing light is placed at the beginning of the barrier run and at the breakpoint where the barrier becomes parallel to the roadway.
For worker visibility, the MUTCD “requires the wearing of high-visibility safety apparel that meets the Performance Class 2 or 3 requirements of the ANSI/ISEA 107-2004 publication entitled American National Standard for High-Visibility Safety Apparel and Headwear.” Because of the higher number of work-zone crashes occurring on low-speed roadways, and the fact that more workers are struck by construction equipment in work zones than by motorists, the department made the decision to require the wearing of ANSI/ISEA Class 3 garments for workers at all times. In addition, workers who install, make adjustments to, or remove temporary traffic-control devices at night (30 minutes prior to sunset to 30 minutes after sunrise) are required to wear Type E full-length trousers, providing for maximum visibility of workers during one of the most hazardous activities related to roadwork. This requirement also applies to flaggers performing night operations.
In addition to improved standards in the VWAPM, we also have incorporated information not shown in Part 6, namely temporary traffic control for roundabouts, slow-roll TTC application, placement of law enforcement in lane closures and standardization of PCMS messages for each typical traffic-control application.
The improved standards and guidance required by the VWAPM has been derived over the years from recommendations by field forces and our industry partners, conversations with other state DOTs on their work-zone requirements, and from annual project reviews performed by VDOT and FHWA staffs. Have these stronger requirements helped in reducing crashes, injuries and fatalities to motorists and workers? We believe by providing bigger, brighter and closer-spaced temporary traffic-control devices, we’ve given our employees and contractors the tools needed to safely repair and maintain the nation’s third-largest state-maintained roadway system. ST