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SECTION V--DESCRIPTION OF STRATEGIES Objective 19.1 C--Improve Work Zone Design Practices Changes in the basic approach used to design work zones and the specific design features included in work zones provide a number of opportunities to improve overall safety and reduce the risk of fatalities. Agencies can best ensure consistently high-quality work zone designs by developing and implementing specific design guidance and procedures for use by designers and planners. Design features intended to reduce the risk and consequences of work space intrusions and to accommodate the needs of other roadway users can contribute to the overall safety of work zones. Greater attention to the design of work zones may enhance some of the other objectives proposed in the guide. It may lead to a more efficient overall operation of the work zone, in terms of both traffic operations and safety. 19.1. C1--Establish Work Zone Design Guidance (T) General Description Experience shows that inappropriately designed work zones are common. Work zone design guidance has been established in some states, but other states do not have set guidelines for designers to follow. Adoption of design guidelines is an initial step to ensuring a level of quality and consistency in work zones under an agency's jurisdiction. Periodic updating of work zone design guidelines is recommended to ensure that the latest knowledge related to work zone safety is reflected in the guidelines. Work zone conditions differ from normal driving conditions. Drivers familiar with a roadway encounter different conditions when driving through work zones, and violations of driver expectancy may result. Space limitations, when combined with the challenge of configuring a work zone to allow continuation of traffic operations while work is underway, often result in less than ideal geometry. In addition, since every situation is different, it is common to have a significant amount of variation in design among work zones. Designing work zones according to established guidelines for layout geometry and use of materials will contribute to meeting driver expectations by providing consistency between work zones, resulting in less violation of driver expectancy and safer work zone operation. Several examples of design elements for which guidelines would be desirable are: Lane transitions. Ideally, lane transitions would be designed so as to reduce or eliminate uncomfortable deceleration as well as speed variance in the work zone. While optimum transitions are desired, it is not always possible to implement them due to existing constraints in the project area. Lane widths. Designers would benefit from information on which to base selection of lane width for a specific project. Ingress and egress of work vehicles. Guidelines for providing space for acceleration and deceleration of trucks as they enter and exit the work zone, as well as for provision of periodic interruption of traffic in at least one lane, would be useful. Pavement edge drop-offs. Guidance on use of signs, channelizing devices, or barrier can help designers provide more consistency in work zones (see Appendix 6). V-67

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SECTION V--DESCRIPTION OF STRATEGIES NCHRP Project 3-69 is developing a methodology to help transportation professionals choose appropriate design and traffic control elements for work zones on high-speed roadways. This is expected to be completed in 2006. EXHIBIT V-19 Strategy Attributes for Establishing Work Zone Design Guidance (T) Attribute Description Technical Attributes Target The principal target of this strategy is the agency designer who will develop plans for the work zone. Proper design guidance is expected to affect all types of work zone crashes by reducing road user and worker exposure to potentially unsafe work zone conditions. This is done by developing and applying design guidelines to ensure safe design practices and consistency among work zones. A wide variety of project types, including both construction and maintenance operations, would benefit from being designed according to established guidelines. Expected Effectiveness It is expected that establishing and using work zone design guidelines will improve work zone safety, though it is not feasible to do a valid measurement of an impact from a support function that is somewhat removed from the road operation. Providing easily accessible materials can promote the awareness of staff with agency policies and procedures. Keys to Success A key to the success of this strategy would be conduct of (1) quality-control reviews to ensure that work zones are designed properly and (2) safety audits or inspections of the work zones to ensure that they are installed as planned. Agency personnel should receive training in any newly adopted design guidelines. Staff who do not design work zones frequently may need to repeat training when those skills are needed. Potential Difficulties Review of work zone designs and inspections of work zones will increase the workload on agency staff who would be assigned responsibility for these tasks. To address potential liability concerns and provide a basis for future decisions made during the development of work zone design, guidelines should be documented so that a record is kept of (1) the information used to develop the guidelines, (2) decisions on what to include or leave out, and (3) discussions on various topics. Appropriate Measures Process measures would include the existence of the design policies, the frequency of and Data review of these policies, and the number of work zone projects to which they are applied. It is not feasible to measure the safety effectiveness of this type of support activity. Impact should be measured, instead, in terms of the improvement in safety- oriented design features of work zones. Associated Needs None identified. Organizational and Institutional Attributes Organizational, Support for this effort is best attained from the highest levels in the agencies to Institutional and improve agencywide acceptance and implementation of new guidelines. It is also Policy Issues important to involve all interested parties within an agency in developing guidelines, or at least in planning discussions and review efforts. Ultimately, it is desirable that the design guidelines be adopted as agency policy. V-68

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SECTION V--DESCRIPTION OF STRATEGIES EXHIBIT V-19 (Continued) Strategy Attributes for Establishing Work Zone Design Guidance (T) Attribute Description Interagency agreements may be needed in order to ensure participation of people outside the highway agency with interest in work zone safety, such as police departments. Issues Affecting Implementation may take some time, since development of the guidelines may require Implementation Time research into work zone safety and operations issues, the state of the practice, and federal and other agency policies. Guidelines would also need to undergo an extensive review within the agency, including a review by risk management personnel. Costs Involved A key cost is the personnel time that would be needed to develop and review the guidelines. Publication of the guidelines (whether in printed or electronic format) and development of training for agency personnel and contractors should be considered when estimating development costs. The cost to develop guidance could be significant, but per-project cost would be low. Training and Other Agency personnel should be trained in the application of the design guidelines, as Personnel Needs should personnel from any contracted organizations that will be designing work zones. Legislative Needs None identified. Other Key Attributes Compatibility of This strategy is compatible with the others discussed in this guide. Strategy 19.1 F4, Different Strategies regarding safety inspections, is directly related to this strategy. Information on Current Knowledge Regarding Agencies or Organizations That Are Implementing This Strategy Several agencies have their work zone design guidance traffic control manuals available online: Illinois DOT's Virginia Work Area Protection Manual: http://www.dot.state.il.us/desenv/bdemanual.html. Indiana DOT's Design Manual: http://www.in.gov/dot/div/contracts/standards/dm/. Virginia DOT's Work Area Protection Manual: http://www.virginiadot.org/business/resources/1-%20WEBwapmCOVER.pdf. Washington State DOT's Design Manual: http://www.wsdot.wa.gov/fasc/EngineeringPublications/manuals/Designmanual.pdf. In an effort to improve design and operation of future work zones, Oregon DOT holds a debriefing meeting at the end of construction projects. Oregon DOT is also looking into developing a traffic control plan database and providing traffic control plan development training for staff and consultants in order to facilitate statewide consistency. V-69

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SECTION V--DESCRIPTION OF STRATEGIES 19.1.C2--Implement Measures to Reduce Work Space Intrusions (and Limit Consequences of Intrusions) (T) General Description Vehicles traveling through work zones are near workers, work activities, and equipment in the work space. Work space intrusion crashes may occur when vehicles for one reason or another leave the traffic space and enter the work space. These crashes have high potential for resulting in severe injuries or fatalities, especially for workers not inside construction vehicles and occupants in vehicles colliding with heavy equipment. Bryden et al. (2000) found that intrusion crashes represent approximately 9 percent of all work zone crashes. Many factors can contribute to these crashes, including excessive speed, driver fatigue, impairment, inattention, reduced visibility, adverse weather, conflicts with other vehicles in the traffic space, or inadequate traffic control. Positive protection is defined as a device that contains and redirects vehicles in accordance with NCHRP Report 350, thereby preventing vehicles from intruding into the work space. Providing positive protection separation between the traffic and the work space, while not always achievable, has the potential to reduce crash frequency and severity for both workers and road users. NCHRP Project 20-7, Task 174, produced a final report on the use of positive protection in work zones (copies of this final report are available upon request from the NCHRP). When physical barriers cannot be provided, it is imperative to provide the necessary measures to keep drivers alert and traveling at an appropriate speed. Strategies to reduce work space intrusions where positive protection cannot be used are based on improving the visibility of the work space, increasing driver awareness of the work zone, reducing speeds, and reducing roadway departures. While these treatments cannot physically prevent an intrusion, such measures may reduce the risk of an intrusion event occurring. It is important to note that not all work space intrusions can be eliminated. In such cases, it is imperative that the consequences of such an intrusion, especially to the workers within the work zone, be limited. Physical Separation Measures Methods for reducing work space intrusions include: Portable concrete barrier, Shadow vehicles with or without truck-mounted attenuators or arrestor nets, and Vehicle arrestor barriers. Providing physical barriers that separate traffic in the active lanes from the transition area, work space, and/or buffer space is the cornerstone in positive protection. In nearly all cases, such barriers eliminate the possibility for intrusion into the respective work zone areas. Portable concrete barriers are the preferred barriers for such protection. Water-filled barriers can be used for some of the same applications as portable concrete barriers and can be easier to move. Low-speed roadways and situations where deflection control is not critical are examples of where water-filled barriers may be appropriate. Moveable barriers may be a good physical separation option in situations where a lane can be or needs to be closed and reopened frequently. An example of a situation where this may V-70

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SECTION V--DESCRIPTION OF STRATEGIES be appropriate is when there is a significant difference in the peak volume traveling in each direction through a work zone. A lane can be closed in the off-peak period and reopened for the peak period in that direction of travel. Also, moveable barriers may be appropriate for nighttime projects in which a lane needs to be closed on a nightly basis. Application of moveable barriers is discussed in the MUTCD, Part 6H, Typical Application 34 (http://mutcd.fhwa.dot.gov/pdfs/2003/Ch6H.pdf). Speed Control Measures Excessive speed is a significant contributor to intrusion accidents. During construction, space to which traffic can be diverted is often limited. In many cases, the design of the temporary traveled way uses design criteria applicable for lower design speeds in order to maximize the space available for the respective traveled way. Lane shifts and median crossovers usually require vehicles to travel at significantly lower speeds due to shorter tapers and sharper curves. A barrier will often be placed near the traveled way as well, providing less room for errant vehicles going off the traveled way. The applications of low- speed design criteria demand that every effort be made to reduce the speed with which vehicles travel through the work zone. The implementation of measures to reduce such speeds can consequently reduce the number of speed-related intrusion crashes. Such measures include speed limit reductions, police enforcement, drone radar, rumble strips, variable message signs, and pilot vehicles. Pilot cars may be used to lead drivers through the work zone and to help drivers follow flagger instructions. An advantage to using pilot cars is that they can control the speed of the vehicles proceeding through the work zone and provide a form of positive guidance to assist drivers in navigating the work zone. Pilot cars are more feasible in long work zones than in short ones. Intrusion Mitigation Measures Strategies to limit the consequences of work space intrusions include intrusion alarms and spotters/flaggers. Intrusion alarms provide an audible warning to workers when a vehicle enters the work space. The purpose is to provide workers with an additional window of time to move to a safer location. Alarms can sound warnings when impacted or when a detector is triggered. The alarm device can detect the intrusion using infrared beams, microwave beams, or pneumatic tubes. Intrusion alarms are either stand-alone or attached to cones, plastic drums, and other channelizing devices used to separate traffic space from work space. Flaggers can also be provided with alarms to sound if a vehicle disobeys the signal and enters the work zone. Several alarms can be used together to provide warning over long distances. Positive Guidance Measures Channelizing devices, such as drums, can be used to separate a work area from traffic. This does not, however, provide a physical barrier between the traffic lanes and the work area. Reducing the spacing of the devices provides additional positive guidance for drivers. Wider gaps in devices can be used to allow work vehicles to enter and exit the work space. V-71

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SECTION V--DESCRIPTION OF STRATEGIES EXHIBIT V-20 Type III Barricade Spaced at Intervals in Closed Lane to Reduce Intrusion Risk EXHIBIT V-21 Strategy Attributes for Implementing Measures to Reduce Work Space Intrusions (and Limiting Consequences of Intrusions) (T) Attribute Description Technical Attributes Target Implementation of measures to reduce work space intrusions targets crashes involving traffic intruding into the work space and/or buffer space. Such crashes include those of vehicles striking work vehicles, construction equipment, workers on foot, excavations, unprotected bridge dropoffs, bridge piers, falsework, and any other construction feature. This strategy is applicable to any work zone, as it is always desirable to separate traffic from work. Short-duration work zones may not offer cost-effective applications of the more expensive methods of preventing intrusions, such as portable barriers. Expected Effectiveness Experience has shown that measures to reduce work space intrusions have been very effective. The use of portable concrete barriers as a physical separation between the active travel lanes and the work zone areas can eliminate most intrusions. Truck- mounted attenuators are also effective in developing positive protection through the work zone. One must remember that a collision with a portable concrete barrier or truck-mounted attenuator is a crash also and may involve damage and injury. However, the resulting damage and injury is expected to be of a lesser degree than not providing this positive protection. The effectiveness in speed reduction strategies is often minor or relatively short-lived, but there may be some benefit in increasing driver awareness of the work zone. V-72

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SECTION V--DESCRIPTION OF STRATEGIES EXHIBIT V-21 (Continued) Strategy Attributes for Implementing Measures to Reduce Work Space Intrusions (and Limiting Consequences of Intrusions) (T) Attribute Description Keys to Success Guidance on the use of positive protection may be needed for the agency that is investigating use of the strategy. An example of one DOT's guidance can be found online at http://wzsafety.tamu.edu/files/guideline.stm. Devices used for positive protection should be maintained. Regular inspections of the work zone should be performed to determine if any repositioning or repairs are needed. Visibility of any devices used to control the speed of traffic is a key issue. When flaggers are used in work zones for speed reduction, improving the visibility of the flaggers can further assist drivers in identifying and reacting to areas of slowed or stopped traffic (see Strategy 19.1 B3). Potential Difficulties It is often not possible to provide positive protection for the entire length of a work zone. Access to and from the active travel lanes may be required intermittently throughout the area of construction for construction vehicles, thereby leaving those areas vulnerable to intrusion from vehicles in the active lanes. In addition, the use of portable concrete barriers may contribute to increased severity of crashes between through traffic vehicles when one vehicle side swipes the portable concrete barriers and is consequently deflected into an adjacent travel lane. With portable concrete barriers in the clear zone, run-off-road crashes will be more likely, since there will be less recovery space for errant vehicles. Some studies have recommended the use of portable concrete barriers only when absolutely necessary to provide protection from a sensitive area in the work zone. Portable concrete barriers are not practical for short-term work zones, especially where the location of the work changes frequently (as with resurfacing projects). Placement and removal of portable concrete barriers involves risk for both workers and traffic. It is possible for water- or sand-filled drums or cones to be misused by not using the proper amount of ballast and/or not placing it in the proper position filled or anchored. This misuse would prevent the devices from performing as designed and could create a hazard if struck by a vehicle. The implementation of truck-mounted attenuators will not eliminate intrusion crashes, and collisions with truck-mounted attenuators can result in serious injuries. As noted previously, the purpose of the shadow vehicle with a truck-mounted attenuator is to stop an intruding vehicle in a controlled manner before it strikes workers or encounters more serious hazards. There are instances where a vehicle will penetrate portable concrete barriers and enter the work space. Experience with both portable concrete barriers and truck-mounted attenuators shows both devices to be very effective in stopping or controlling errant vehicles without high risks to vehicle occupants. However, when impact conditions exceed the design capability of the devices, more serious consequences may result. Devices used to limit the consequences of intrusions should not be placed so that they adversely affect sight distance in the work zone, create additional visual clutter, or confuse drivers. Workers must find intrusion alarms credible. Too many false alarms will significantly lessen the value of the alarms since workers may begin to ignore them. The intrusion alarms need to differentiate between work vehicles entering the work space and actual intrusions by errant vehicles. V-73

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SECTION V--DESCRIPTION OF STRATEGIES EXHIBIT V-21 (Continued) Strategy Attributes for Implementing Measures to Reduce Work Space Intrusions (and Limiting Consequences of Intrusions) (T) Attribute Description Appropriate Measures A key process measure is the number or percentage of projects on which this strategy and Data is implemented, along with the type of method used and the manner in which it is deployed. Key safety effectiveness measures include crash frequency and severity, by type of crash. It is especially important to identify crashes related to the protection measures themselves. These might include side-swipe crashes with the portable concrete barriers or crashes caused by drivers making erratic maneuvers as they (1) get too close to or are deflected from the portable concrete barriers or (2) attempt to avoid entering the work zone. Crash frequency and severity data are needed to evaluate the construction operation for safety effectiveness. Traffic volume data are needed to represent exposure, including changes in volumes on alternative routes during the construction. Associated Needs A PI&E campaign may be needed if a project will involve use of a new device that may cause driver confusion. Organizational and Institutional Attributes Organizational, Portable concrete barriers effectively protect the work zone from traffic intrusion, but Institutional and they can contribute to the occurrence of collisions in the traffic lanes. Agencies may Policy Issues need to evaluate this issue in greater detail to establish appropriate policies and guidelines for the application of portable concrete barriers. Speed control measures that include special law enforcement efforts will need to be carefully arranged and coordinated with the appropriate agencies, including provision for space in which law enforcement vehicles may be placed for surveillance, as well as for stopping violators without negatively affecting traffic operations. Issues Affecting It may take several months to develop guidelines for the use of the various means Implementation Time for achieving positive protection and limiting the consequences of intrusions. Once guidelines are in place and agency personnel have been trained, actual installation time of positive protection devices will be short, but will vary depending on the specific devices used. Installation time for some devices, like intrusion alarms and drums or cones that improve the positive guidance, will be relatively short. Costs Involved Costs would include development of the guidelines, distribution of the guidelines, and training. Installation costs will vary depending on the devices or procedures used. Costs for intrusion alarms and other equipment can be relatively low. However, cost of portable concrete barriers, shadow vehicles, truck-mounted attenuators, and some of the other measures may add significantly to construction costs. Since the devices can be used on other projects as well, the safety benefits can be expected to outweigh the costs. Police enforcement of speeds and other traffic laws in work zones can be funded by the transportation agency or the police department. Federal funding for enforcement may also be available. Training and Other Positive protection guidelines, intrusion alarms, and other methods for reducing Personnel Needs intrusions or limiting the consequences of them should be covered in agency training on work zone design and traffic control. Training on the proper uses for and setup of equipment used for these purposes should be provided to agency personnel and contracted workers. Legislative Needs None identified. V-74

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SECTION V--DESCRIPTION OF STRATEGIES EXHIBIT V-21 (Continued) Strategy Attributes for Implementing Measures to Reduce Work Space Intrusions (and Limiting Consequences of Intrusions) (T) Attribute Description Other Key Attributes Compatibility of Reducing work space intrusion and limiting the consequences of intrusions are Different Strategies strategies compatible with other improvements to work zone safety. Key References Bryden, J.E., L.B. Andrew, and J. S. Fortuniewicz, "Intrusion Accidents on Highway Construc- tion Projects." Transportation Research Record 1715. Transportation Research Board. 2000. Daniels, G., S. Venglar, and D. Picha, Feasibility of Portable Traffic Signals to Replace Flaggers in Maintenance Operations. Texas Transportation Institute. TTI Report 3926-1. 2000. http://tti.tamu.edu/documents/3926-1.pdf. Federal Highway Administration, Intelligent Transportation Systems in Work Zones: A Cross Cutting Study. Report No. FHWA-OP-02-025. Washington, D.C. 2002. http://www.itsdocs.fhwa.dot.gov/JPODOCS/REPTS_TE/13600.html. Federal Highway Administration, Manual on Uniform Traffic Control Devices (MUTCD). Washington, D.C. 2003. Kochevar, K.J., "Intrusion Devices - New and Emerging Technology in Worker Safety." Presented at Making Work Zones Work Better Workshop Series. Federal Highway Administration. http://ops.fhwa.dot.gov/wz/workshops/originals/Ken_Kochevar_ID.ppt. NCHRP Project 20-7, Task 174, final report. "Use of Positive Protection in Work Zones." Available upon request from the NCHRP. New York State DOT, Guidelines for Work Zone Intrusion Countermeasures. 1999. http://wzsafety.tamu.edu/files/guideline.stm. 19.1 C3--Improve Work Zone Safety for Pedestrians, Bicyclists, Motorcyclists, and Heavy-Truck Drivers (T) General Description Work zones should continue to accommodate the road users who were using a roadway before construction began. Work zones present additional workload not only to drivers of passenger vehicles and heavy trucks, but also to pedestrians, bicyclists, and motorcyclists. In addition to providing well-designed facilities for these other road users, agencies should notify drivers of the presence of these people and vehicles and design the work zone for drivers to be able to see and avoid these users. Accommodation of pedestrians, bicyclists, motorcyclists, and heavy-truck drivers should be planned before work begins. In addition, regular inspection of conditions for these road users should be performed in order to ensure that these users are being accommodated safely. V-75

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SECTION V--DESCRIPTION OF STRATEGIES Roadway sections in work zones open to public travel should be free from surface irregularities and construction debris that present hazards to any road user expected. Uneven and cluttered surfaces can cause motorcyclists or bicyclists to fall and can present tripping hazards to pedestrians. This includes pavement edges, large or deep ruts, metal plates, and pavement and other surfaces with low skid resistance. The travel path should be continuous and hard. Loop detectors on existing roadways should continue to be accessible during the project. Additional strategies beyond those briefly discussed in this section are covered in other volumes of the NCHRP Report 500 series: Pedestrians (Volume 10) Bicycles (forthcoming) Motorcycles (Volume 18) Heavy-truck drivers (Volume 13) Pedestrians The MUTCD should be consulted for information on accommodating pedestrians in work zones and on reducing pedestrian-vehicle conflicts. In addition, many of the strategies for improving pedestrian safety discussed in Volume 10 (relating to pedestrian crashes) of this series can be applied to work zones. Careful consideration should also be given to the needs of pedestrians with disabilities, especially when there is evidence that the regular users of this area include pedestrians with special needs. The level of accessibility of existing pedestrian facilities should be maintained during the work period to the extent practical. The MUTCD provides guidance on providing accessible facilities in work zones, including consideration of pedestrians with either visual or mobility disabilities. The changes made to a pedestrian's path, due to work zones, will interrupt the routine of a person with visual disabilities whose route goes through the affected area. Visually impaired pedestrians need clear guidance through the work zone, and this can be provided through detectable obvious barriers and edges on channelizing devices, guide rails, audible warning devices, or even audible spoken messages activated by push buttons. Several treatments that affect pedestrian safety are detailed below. Pedestrian Paths: Pedestrian paths should be continuous, smooth, hard, and located out of hazardous areas. Chadda and McGee (1984) discuss pedestrian considerations in work zones. Maintaining pedestrian access to adjacent properties throughout construction may be required. While undesirable, it may be necessary for practical reasons to allow for pedestrian travel through the work zone. If pedestrian travel paths will be obstructed or made more hazardous by ongoing work, the traffic control plan should provide an alternative, safer route. This may be accomplished with: Existing pathways: pedestrians can be directed to use alternative pathways already existing in the work zone. This may include sidewalks on the other side of the street. Bypasses: temporary bypass routes can be provided where unobstructed and nonhazardous space is available in the right-of-way. Bypasses may be established in parking lanes or grass buffers in the work zone. V-76

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SECTION V--DESCRIPTION OF STRATEGIES Detours: pedestrians can be instructed to use a detour route when it is not possible to use other existing pathways Traffic Plans: When establishing pedestrian traffic plans, the origins and destinations of the pedestrians should be considered, as well as the ideal (typically shortest) routes though the work zone. Access to bus stops and cross walks should be maintained, or temporary relocation of both should be considered. Pedestrians will be using the paths during all lighting and weather conditions; therefore, messages (both visual and audible) should be clear at all times. The FHWA Office of Safety website has a checklist of pedestrian-related items to consider when developing a traffic control plan: http://safety.fhwa.dot.gov/wzs/sa03047/wzp3.htm. Channelization: Pedestrians should be encouraged to use the safest path and to cross roadways in the appropriate location. One way to accomplish this is through channelization, which can help reduce conflicts with work activities and vehicular traffic. Any devices or barriers used to channelize pedestrian movements should not obstruct the sight distance for motorists. Barriers can also serve as protection from vehicular traffic when the two travel paths are close. Public education: Educating pedestrians on appropriate behaviors when walking through work zones, as well as on the meanings of traffic control devices, can contribute to their safe use of pedestrian facilities in work zones. FHWA has several pedestrian information sheets, one of which covers walking through work zones: http://www.tfhrc.gov/safety/pedbike/issues/issues.htm. The pedestrian guide (Volume 10 of this series) discusses strategies for improving pedestrian safety in more detail. EXHIBIT V-22 Work Zone Pedestrian Walkway V-77

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SECTION V--DESCRIPTION OF STRATEGIES Bicyclists Consideration should be given to the needs of bicyclists as work zones are being designed and set up and as work is being performed. Pavement edge dropoffs or longitudinal joints can present hazards to bicyclists, as can surface debris and low-traction areas. Warning signs increase driver awareness of bicycles in work zones. Standard MUTCD bicycle warning signs should be used to alert drivers to the presence of bicyclists. PennDOT installed orange warning signs to inform drivers that bicyclists may be using the travel lanes in a construction zone with heavy bicycle traffic. The "Bicycles in Roadway" signs have flashing lights to increase their visibility and are supplemented with changeable message signs at the ends of the work zone. (Additional information can be found online at http://www.222connections.com/lehigh/ news_story.cfm?news_item=48). The bicycle guide (forthcoming in this series) will provide details on improving safety for bicyclists. Motorcyclists Many of the work zone design features that improve safety for drivers of passenger cars and trucks will improve safety for motorcyclists. One example is paved shoulders, which can be used by motorcycles in case of break downs, as well as other vehicles. Motorcycles should be explicitly considered when making decisions about other design features, such as barrier type, and pavement marking materials that could reduce traction. Temporary pavement marking materials can be shorter or provide a gap free of the material for motorcycles to pass through in order to reduce low-traction surfaces. Sewer caps that temporarily sit above the pavement level, edge drop offs, and other surface conditions commonly found in work zones can present more significant hazards to motorcycles than other vehicles. Agencies may wish to require that longitudinal joints be closed up once work is completed for the day. Advance warning signs can be used to inform motorcyclists of conditions in the work zone, such as wet pavement, longitudinal joints, or steel plates in the roadway. Refer to the motorcycle guide (Volume 18 of this series) for additional details on these and other strategies. Heavy-Truck Drivers The physical and operational characteristics of heavy vehicles vary from those of passenger cars and should be considered in work zones on roadways where trucks typically travel. Several heavy-truck characteristics to consider include: Acceleration and deceleration capability: This plays a role in many aspects of a work zone design and its operation. Temporary entrance and exit ramps and flagging operations are two examples. Restriction of trucks to the right lane of a multilane roadway may not be desirable if there are entrance and exit ramps within the work zone. Rollover potential: Design of radii on ramps, crossovers to temporary roadways, and lane shifts should consider the higher center of gravity of trucks. V-78