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6Law enforcement agencies employ a range of techniques and strategies as part of their normal traffic enforcement duties. Most of these strategies are appropriate for use in work zone locations as well. In addition, several unique enforcement approaches or strategies exist to address unique challenges of some of the work zone situations listed herein. Basic Enforcement Philosophies Overt Versus Covert Enforcement Strategies Generally speaking, traffic enforcement efforts are overt or covert in nature. Overt enforcement strategies emphasize vis- ibility through the use of marked patrol vehicles and officers positioned in full view of approaching traffic, the use of emer- gency vehicle warning lights, and sometimes even advance notification about the location and time of enforcement via the media or advance warning signs. Some departments also instruct their officers involved in overt enforcement activi- ties to turn on their radar units as an additional method of announcing their presence in the area. Conversely, covert enforcement strategies are performed in relative obscurity with unmarked vehicles or marked vehicles parked and par- tially hidden from view. Whereas the intent of overt enforce- ment is to maximize driver awareness that enforcement is present, the goal of covert enforcement tactics is to create the sense among drivers that enforcement may be present at any location and time. It is believed that if drivers do not know when and where enforcement is present, they will better regu- late their driving behavior over the entire highway system at all times. Studies comparing the effectiveness of overt versus covert enforcement, and those comparing the behaviors of drivers with and without radar detectors, tend to support this line of thinking (2, 3). Overt strategies do attract considerable attention of pass- ing motorists. Care should be taken to position officers and their vehicles at the work zone where this attention will not adversely affect driving behavior, such as at critical merge or diverge locations, key decision points, etc. Cooperative Versus Dedicated Enforcement Efforts When discussing work zone enforcement efforts, it is important to distinguish between cooperative and dedicated enforcement activities. Cooperative enforcement is provided as part of normal enforcement agency operations if officers are available. Officers are usually on regular duty and not overtime. Usually, cooperative enforcement is not reimbursed by the highway agency. In contrast, dedicated enforcement involves officers who are specifically hired for, or assigned to, a work zone for the shift, and are not available for other non work zone assignments unless an extreme emergency situa- tion arises. Officers on dedicated enforcement assignments are often on overtime pay (but not always), and the enforce- ment agency is typically (but not always) reimbursed for their costs by the highway agency. In many locations, a combina- tion of cooperative and dedicated enforcement efforts is used in highway work zones. Active Enforcement Versus Presence-Only (i.e., Traffic Calming) Strategies Within work zones, many highway agencies make the dis- tinction between law enforcement efforts to identify, pursue, and cite traffic law violators, versus efforts to increase driver attention, reduce speed, and generally calm traffic in the vicin- ity of the enforcement vehicle. In a traffic-calming mode, enforcement personnel usually remain at a location with or without lights flashing, but do not actively engage in identify- ing traffic violators and then pursuing and issuing citations. Nationally, there is support and opposition for both approaches. The support for the active enforcement approach (and opposition for the traffic-calming approach) generally C h a p t e r 2 Traffic Enforcement Strategies for Various Work Zone Situations
7 comes from state DOT office and enforcement agency per- sonnel who believe the potential threat of citation must be maintained at all times to avoid a loss of enforcement agency credibility with the motoring public. There have been anec- dotal comments by some agencies that extensive reliance on traffic-calming enforcement practices has resulted in a lack of driver response to enforcement vehicles over time. Conversely, support for the traffic-calming enforcement strategies in work zones tends to come mainly from highway agency field personnel and highway contractors. These groups note that when enforcement personnel engage in pursuit of a traffic law violator to issue a citation, the traffic-calming effect of the enforcement vehicle is no longer present where the enforce- ment vehicle was originally located. For work zone situations where the traffic-calming effect is desired at a particular loca- tion, such as near where work crews are working in a closed travel lane without positive protection between them and traffic, the constant pursuit of traffic violators significantly reduces the desired traffic-calming effect of enforcement in the vicinity of that work crew. Many agencies employ a combination of the two approaches depending on the work zone situation of concern. However, there are some entities that strictly employ either one approach or the other in its work zones. Recent studies to evaluate such an exclusive practice indicates that drivers do indeed âlearnâ over time that only traffic-calming behaviors are being used (4). However, drivers in those situations also reported that they âlearnedâ to associate the presence of the enforcement vehicle in a work zone with a true need to slow down and be more attentive (i.e., they anticipated the presence of a traffic queue or of workers located close to moving traffic). Field studies further verified that the magnitude of speed reductions upon encountering an enforcement vehicle sitting on the shoulder in a work zone was essentially the same regardless of whether the region relied exclusively on active work zone enforcement or on traffic-calming enforcement presence in work zones (4). Work Zone Enforcement Techniques Several different techniques can be used by enforcement personnel in work zones. The choice depends on the charac- teristics of the work zone, existing traffic behaviors, primary traffic operations and safety concerns, whether the majority of traffic using the roadway is local repeat drivers or non-local through drivers, automobile/large truck mix, and other factors. Stationary Deployment Techniques The most common technique used in work zones is the deployment of an officer and marked vehicle somewhere within or upstream of a work zone adjacent to the travel lanes. If the emphasis is on active identification and citation of traffic law violators, the enforcement officer may choose either an overt strategy by sitting in full view of approaching traffic, or a covert strategy by utilizing an unmarked vehicle or positioning his or her vehicle out of view of oncoming traffic. If the goal is to alert approaching drivers and calm traffic, the officer and marked vehicle are positioned close to the travel lanes with emergency lights flashing in full view. A stationary enforcement vehicle and officer will typically create a greater speed reduction than circulating patrols, but the effect will be localized. Specifically, speeds will be reduced from just before the officer and vehicle to approximately one mile beyond where the officer and vehicle are located (see Figure 3). Therefore, where speed reductions at a spot loca- tion are desired, the officer and vehicle should be positioned a short distance (1000 feet is suggested) prior to where the speed reduction is needed. Although average speed reduc- tions as much as 14 miles per hour (mph) have been recorded, 5 to 7 mph reductions are more common, especially on high- volume, high-speed roadways. Pack Enforcement Strategy In situations where active enforcement efforts (i.e., identi- fication and citation of traffic law violators) are desired, some agencies utilize a pack enforcement strategy. In this case, one enforcement vehicle (marked or unmarked) and officer are positioned to identify traffic law violators. The officer then calls out descriptions and license plate numbers of traffic law violators to one or more officers at a downstream location for apprehension and citation. In this way, the speed reduction and traffic-calming effect of the upstream enforcement vehi- cle is maintained while the active enforcement efforts down- stream contribute to a lasting change in driving behavior. Figure 3. Example of a stationary marked enforcement vehicle at a work zone.
8The advantages of this strategy are the following: ⢠This approach eliminates the pursuit of the violator into and/or through the work zone in order to issue a citation. ⢠This approach maintains the visibility and traffic-calming effect of the upstream enforcement vehicle at a point, since it does not have to leave its location. ⢠This approach means that multiple officers are in the vicin- ity of the work zone in the event of an emergency. The disadvantages of this strategy are the following: ⢠This approach requires the use of multiple officers and vehi- cles. This requirement increases costs and places increased pressure on available law enforcement personnel and equip- ment resources in a region. ⢠Under this approach, the violating vehicle does not get pulled out of the traffic stream until after exiting the work zone. One work zone-specific pack enforcement strategy that sev- eral agencies are using is to âcamouflageâ a law enforcement officer with a flagger vest and positioning the officer and speed- measuring lidar or radar within the work area on or near work equipment. The camouflaged officer identifies a violator and communicates the vehicle description and license plate num- ber to officers stationed downstream of the work zone who apprehend and cite the vehicle. Initially termed âOperation Hard Hat,â it has also been termed âOperation Yellow Jacketâ by some agencies (see Figure 4). Initially, the concept was envisioned to be a covert enforce- ment activity. However, many agencies now alert drivers in advance that this effort is underway in order to achieve better driver response and immediate speed reductions at the tar- geted work zone. This information is provided via media announcements and through portable changeable message signs (e.g., WORKZONE/RADAR/ENFORCED, REDUCE/ SPEED/NOW) upstream of the work zone to increase driver compliance and thus improve safety through the work zone. Queue Protection Strategy Another stationary enforcement strategy employed by some agencies is to position the vehicle and officer approxi- mately 0.25 miles upstream of lane closures where traffic queues are anticipated. The enforcement vehicle and officer serve a traffic-calming and attention-getting function, reduc- Figure 4. Examples of the operation hardhat pack enforcement strategy (Source: Florida and New York State departments of transportation).
9 ing the likelihood of high-speed rear-end crashes between approaching traffic and vehicles already in the queue. As the upstream end of the queue grows or dissipates over time, the officer moves the vehicle along the shoulder to remain approximately 0.25 miles upstream of the queue. The advantage of this strategy is the following: ⢠The traffic-calming effect of the enforcement vehicle is believed to reduce the likelihood of rear-end crashes at the upstream end of the queue, and to reduce the severity of crashes that may occur. The disadvantages of this strategy are the following: ⢠The strategy sometimes requires the officer to move the enforcement vehicle backwards along the shoulder to main- tain a 0.25 mile distance to the queue. ⢠The strategy can only be used where a shoulder exists for the enforcement vehicle to be parked and driven on if necessary. In some work zones, the shoulder is closed or converted to a temporary travel lane, which eliminates this strategy from consideration. Police Traffic Controller Strategy This strategy requires officers to be positioned outside of their vehicles for the purpose of reducing speeds and calming traffic. The officer does not perform specific traffic control duties such as stopping vehicles, indicating to drivers where to travel, etc. Rather, the emphasis is simply on being visible, establishing eye contact, and using other non-verbal commu- nication techniques (such as the âslow downâ flagger hand signal) with the approaching driver. The advantages of this strategy are the following: ⢠The visibility of the officer outside of the enforcement vehicle establishing eye contact with approaching drivers can result in significant speed reductions. ⢠This technique does not require the use of an official enforcement vehicle, which can reduce costs (however, some enforcement agencies may require the officer to uti- lize an enforcement vehicle and still require payment for its use in this situation). The disadvantages of this strategy are the following: ⢠Being out of the vehicle, the officer is placed at increased risk from approaching traffic. ⢠The officer cannot easily initiate pursuit of any vehicle deemed a âsignificant hazardâ by the officer (e.g., driving while severely impaired, engaging in a speeding contest, etc.). Circulating (or Mobile) Enforcement Techniques Circulating patrols through the work zone can be accom- plished in both marked and unmarked vehicles, depend- ing on whether overt or covert enforcement activities are desired. As with stationary techniques, the effect of circulat- ing patrols on speeds is most pronounced in the immediate vicinity of the enforcement vehicle (which is moving along the roadway section). However, the average speed reductions achieved with this technique tend to be somewhat smaller (on the order of 2 to 4 mph) than those achieved with sta- tionary techniques. This effect can vary depending on the deployment schedule utilized. For example, a circulating patrol at the posted work zone limit on a two-lane road- way effectively limits the speed of the traffic stream to the speed of the enforcement vehicle and discourages passing by higher speed vehicles. For work activities that are occur- ring immediately next to the travel lanes, this approach can reduce speeds next to the work crew, which is believed to improve overall worker safety. Although the majority of circulating patrols rely on enforce- ment vehicles, a few agencies have utilized fixed-wing aircraft or helicopters as part of their mobile patrol efforts. Obviously a covert enforcement activity, aircraft patrols identify poten- tial speed violators on a facility and time the suspect between marked locations on the roadway. If the elapsed time is too fast, enforcement personnel in the aircraft notify an officer and vehicle on the ground to actually stop the violator and issue the citation. This technique is relatively expensive to operate, and so is used infrequently. The advantages of this strategy are the following: ⢠Continuous circulation of the enforcement vehicle does not allow drivers to limit their speed reductions to a specific loca- tion where they âknowâ the officer is located (either through experience or by communication with other motorists in the vicinity) ⢠The circulating enforcement patrol can simultaneously serve a roadway monitoring and incident detection/response role, helping to identify drivers in need due to stalls, no fuel, etc. The disadvantages of this strategy are the following: ⢠The influence of the enforcement vehicle varies by loca- tion as it traverses the roadway, making this technique less useful for work zone situations that benefit from a speed reduction and increased driver awareness at a particular spot (e.g., entering a work zone lane closure, passing by a road work crew, etc.). ⢠The use of aircraft for enforcement is costly.
10 Automated and Semi-Automated Speed Enforcement Techniques Presently, the Illinois DOT, the Washington State DOT, and the Maryland State Highway Administration (MDSHA) all utilize semi-automated speed enforcement technology to electronically identify violators in work zones and to capture an image of the vehicle embedded with speed, location, date, and time information about the violation. The agency then determines the registered owner of the vehicle via the license plate number, and issues a citation in the mail. In the semi- automated approach used in Illinois and Washington, an offi- cer operates the equipment from inside a specially-marked van (see Figure 5). The officer is thus present to verify that the vehicle selected was indeed in violation of the speed limit (plus an additional tolerance), which allows the citation to remain a moving vehicle violation as is the case for traditional speeding citations. The citation is still mailed to the owner of the vehicle. In most states, specific legislation must first be passed to allow this technology to be used. In Illinois, the legislation required additional signing to be provided in advance of the work zone when the van is present. In addition, the van itself includes a driver feedback display to indicate the measured speed of the approaching vehicle. If the vehicle still continues to speed exces- sively past the van, a photograph with the pertinent violation information is combined into an encrypted file for further pro- cessing and citation issuance. Tests indicate that speeds in the vicinity of the enforcement vehicle reduce 3 to 6 mph. The advantages of this strategy are the following: ⢠The technology eliminates the need for an officer to pursue and cite the traffic law violator at the time the violation is observed, or to use multiple officers in a pack arrest strategy. ⢠Because no pursuit is required, a higher number of cita- tions can be issued. To counteract this, some states require that a substantial (i.e., 12 mph) tolerance over the work zone speed limit be granted before issuing a citation. The disadvantages of this strategy are the following: ⢠Specific legislation authorizing the use of this technology is required. ⢠Those operating the equipment must be specially trained in order to ensure the legality of the citations. ⢠The equipment is relatively expensive. In Illinois, the amor- tized cost of the van, equipment, and training was $2,950 per month. In addition, there was a cost of an officer to operate the system. However, these costs may be offset somewhat by the higher citation rate that can be achieved. Deciding When Enforcement Is Needed It is important that specific reasons for providing enforce- ment at a work zone exist and can be articulated by the affected stakeholders (the highway agency, the law enforcement agency, and the highway contractor). Enforcement costs are not insig- nificant, and represent an additional burden on enforcement agency manpower and equipment resources in a region, even when highway agency funds are being used to pay for such efforts. If enforcement is to be used, it should have a specific objective, and the implementation strategy should be consis- tent with that objective. Matching enforcement efforts to the specific needs of the work zone requires consideration of both the characteris- tics of the work zone safety hazard being targeted, and the expected benefits versus costs of enforcement deployment. Considering the Characteristics of the Work Zone Hazard A distinction can be made between those hazards related specifically to work activities (and thus present only at cer- tain times and locations) and those that are related to the Figure 5. Semi-automated work zone speed enforcement in Illinois.
11 geometrics and alignment of the work zone design (and thus present at all times). Work activity-related hazards include: ⢠Temporary closure of shoulders or travel lanes during the work shift, including the creation of any traffic queues that may develop due to the reduction in roadway capacity; ⢠Work activities themselves in close proximity to travel lanes, including during the setup and takedown of other temporary traffic control devices; ⢠Materials and work equipment located close to travel lanes; and ⢠Work area ingress and egress by construction vehicles and equipment. Similarly, work zone geometric and alignment design haz- ards include such things as (5): ⢠Narrowed or closed shoulders; ⢠Narrowed or long-term closures of travel lanes; ⢠Pavement edge drop-offs; ⢠Irregular pavement surfaces and/or uneven joints; ⢠Lane shifts; and ⢠Horizontal curvature at median crossovers or temporary diversions designed to a lower design speed than the pre- vailing or expected travel speeds. Some highway agencies go so far as to require project per- sonnel to formally document when and for what reasons enforcement is desired in the work zone. This request is then reviewed and approval granted if so warranted. An example of a request form is provided in Figure 6. In general terms, the existence of one or more of the fea- tures listed does not imply that work zone enforcement is automatically needed. Indeed, many work zones are safely and successfully completed with these types of constraints without any type of work zone enforcement provided. However, if the work zone planner/designer is concerned about a particular Figure 6. Example of a highway agency work zone enforcement request form. REQUEST FOR USE OF WORK ZONE ENFORCEMENT [Highway Agency] The [name of responsible person at highway agency] or his/her designee must approve any use of [name of enforcement agency] support on a project. Upon approval, such use must also be reported to [name or division within highway agency tracking use of enforcement in work zones]. Justification for Request (check all that apply): Major construction project Full roadway or ramp closure required for roadway maintenance Closure of [one, two, etc.] or more travel lanes on a freeway or expressway [having three or more lanes in each direction] Expectation of queues Night work activity Situations involving temporary traffic flow disruptions (erection of overhead structure, movement of large equipment, traffic signal repairs) An unusual increase in crashes at a location, or work zone design features that require drivers to reduce their speed to safely negotiate (this requires one week of daily [4 hours each] enforcement followed by 3-4 days [4 hrs each] per week) Other ______________________________________________________________ Date of Request______________ Date(s) of Requested Enforcement ________________ Beginning Time _______________ am/pm Ending Time _________________am/pm Project Location __________________________________________________________ Number of troopers requested per shift _____________ Approval: Recommended by ____________________ Approved by ________________________ (district engineer) Date _______________________ Date _________________________ Note: sections in italics may be added to increase specificity if desired
12 feature, or if crashes in a particular work zone increase signifi- cantly in the vicinity of such a feature, the provision of work zone enforcement to modify driving behavior on a continu- ous basis may be appropriate. For work activity-based hazards, the need to provide enforce- ment is dictated by when and how often such work activities are to occur. For these situations, highly-visible stationary enforcement located just upstream of the hazard meets the desired objectives most effectively. As noted previously, these officers and vehicles can operate strictly in a traffic-calming role (without pursuit and citation of traffic violators), as part of a pack enforcement strategy, or with the intent to pur- sue and cite traffic law violators themselves as needed. If the latter strategy is selected, however, the traffic-calming and attention-getting benefits of enforcement at the location of the hazard will be diminished during those times the officer leaves to pursue and cite the violator. For work zone design-related concerns, it will be necessary to establish an active enforcement regime that is substantial enough to achieve a change in driving behavior. Providing only occasional traffic-calming presence or sporadic enforce- ment will generally not suffice. Rather, an initial period of intense enforcement that emphasizes identification, pursuit, and citation of traffic law violators will be required to estab- lish an expectation of increased enforcement presence within the work zone. This emphasis will then lead to a continuous change in driving behaviors (i.e., a speed decrease, heightened awareness) at all times, including those times when enforce- ment is not present. This strategy can be accomplished using either overt or covert enforcement methods (or both), and can involve stationary or circulating patrols. Once this expectation is established, the amount of enforcement provided can be reduced, but still must be maintained at some minimal level to keep drivers from reverting back to pre-enforcement behavior. The saturation enforcement approach has been used as part of the selective traffic enforcement program (STEP) in many states for years. Although definitive minimum enforcement requirements to achieve this type of behavioral change in drivers do not exist for most conditions, studies and anecdotal evidence suggests that providing enforcement in a work zone approximately 4 hours per day for each of 5 days in a row is sufficient to alter driving behavior (6). Once the initial period is completed, enforcement must be provided twice or three times a week (again for about 4 hours per day) to maintain the behavioral change in drivers. This level should be considered a minimum; the level of enforcement on high-volume urban freeways may need to be significantly greater. The actual amount of effort needed will depend on whether most of the traffic on the facility consists of local, repeat drivers who travel the work zone several times a week or of through drivers pass- ing through the work zone infrequently. The law enforcement agency with jurisdiction over the facility will have a good feel for the level of effort that will be required. Considering the Safety Benefits of Enforcement Versus Enforcement Costs Ideally, work zone enforcement would best be used where its benefits equal or exceed the costs of providing that enforce- ment. Other practical considerations, such as the amount of enforcement staffing available, the other enforcement tasks that are deferred in the region in order to provide work zone support, etc., also influence decisions. However, from a sim- ple justification perspective, the expected benefits of using enforcement in a work zone is an improvement in safety in terms of reduced work zone crash costs (although there may be some situations where the traffic-calming effect of enforce- ment could improve traffic flow and result in reduction in motorist delay costs). Unfortunately, it is difficult to assess the crash cost reductions due to enforcement with any certainty. The extent to which enforcement can influence driver behav- ior (and ultimately safety) depends on many site-specific fac- tors such as: ⢠The type of enforcement strategy being employed; ⢠The number of travel lanes, traffic volumes, percentage of local and non-local motorists, and vehicle mix on the facility; ⢠The difference between the work zone speed limit that is posted and the current operating speeds of drivers; and ⢠The type and amount of public information disseminated about the work activity. Other factors, such as various work zone conditions listed earlier, will also influence enforcement effects on motorists. To date, though, specific analyses of the relationship between these factors and crash reductions due to enforcement have not been performed. One study suggested that a 10 to 20 percent reduction in crashes could be reasonably achieved through the adoption of enhanced enforcement efforts in work zones (7); in other studies, the range of crash reductions attributed to work zone enforcement range between 0 and 45 percent (8â10). It should be noted that these values represent overall changes in crash frequencies during a period of time when enforcement efforts were expanded above normal levels. The actual effect that a given enforcement officer and vehicle may have on crash risk when physically present at a location could be even greater. Interestingly, these numbers are not inconsistent with recent research on the safety effects of strategies to reduce vehicle speeds in circumstances other than work zone-related enforcement. According to that research, 5 mph speed reduc- tions on high-speed (60 to 70 mph) roadways can correspond
13 to a 22 to 25 percent reduction in non-fatal injury crashes, and to a 33 to 42 percent drop in fatal crashes (11). Nationally, enforcement costs can also vary widely. A review of interagency agreements in various states found that loaded hourly rates for enforcement ranged from about $25 to $100 per hour per officer (12). Revenues generated through active enforcement efforts in the work zone could possibly offset these costs somewhat, but would not if enforcement is used primarily in a traffic-calming mode (which could be a significant consid- eration when considering the deployment of multiple officers in the work zone at a time for pack enforcement or combined traffic-calming/active enforcement teams). Consequently, the hourly costs depend on both the number of officers used and the method of enforcement desired. The fact that neither enforcement effectiveness nor the actual work zone crash costs expected at a location can be pre- dicted with much precision, coupled with the wide range of possible costs of deploying enforcement in a work zone, makes it difficult to establish definitive criteria as to when enforce- ment can be justified from an economic perspective. As an example, Table 1 illustrates the annual average daily traffic (AADT) values at which various costs of enforcement would be offset by reduced work zone crash costs at a freeway work zone. Two scenarios are considered: ⢠A favorable benefit assessment (enforcement assumed to lead to a 50 percent reduction in work zone crash costs when present, work zone crash costs without enforcement assumed to be at the 95th percentile level of expected costs); and ⢠A conservative benefit assessment (enforcement assumed to lead to a 25 percent reduction in work zone crash costs, work zone crash costs without enforcement assumed to be at the average level of expected costs). Under the favorable-benefit scenario, the use of enforce- ment can almost always be justified, even when enforcement costs are fairly high. For example, enforcement efforts that cost $100 per hour are estimated to be offset by reduced work zone crash costs once the AADT reaches at least 20,000 vehicles per day (vpd) for work operations being performed during the day, and 65,000 vpd if the work operation is being performed at night. Work zone crash costs are lower per hour at night than during the day for a given AADT because most of the traffic flow each 24-hour period occurs during the day. Less expensive enforcement costs correspond to lower AADT thresholds. On the other hand, an assessment based on more conserva- tive assumptions indicates that AADTs must be much higher before a reduction in work zone crash costs will offset the same enforcement cost values. In fact, the AADT values asso- ciated with the highest enforcement cost level would imply that enforcement would almost never be cost effective on freeway facilities, a result that is very counter-intuitive. Over- all, the values in Table 1 highlight the uncertainty associated with this type of analysis. Depending on the assumed cost of enforcement being considered, the break-even AADT level can differ between 15,000 to more than 150,000 vpd under the two different assumptions. Similar comparisons could be performed for other roadway types and work operations, but the same general trends would likely exist. The AADT thresholds shown in Table 1 under the favorable- benefit scenario could be used as an initial guide for justifying enforcement use on most roadway types (recognizing some- what lower AADT values might be justifiable on non-freeway facilities given their typically higher crash rates). In reality, though, available funding, availability of enforcement staff, and other considerations will often limit enforcement use to facilities with higher volumes than those shown. Enforcement Costs AADT Where Enforcement Benefits are Approximately Equal to Enforcement Costs Favorable-Benefit Scenario Conservative-Benefit Scenario $25 per hour Daytime work zone Nighttime work zone 5000 vpd 20,000 vpd 20,000 vpd 45,000 vpd $50 per hour Daytime work zone Nighttime work zone 10,000 vpd 35,000 vpd 35,000 vpd 100,000 vpd $75 per hour Daytime work zone Nighttime work zone 15,000 vpd 50,000 vpd 50,000 vpd 150,000 vpd $100 per hour Daytime work zone Nighttime work zone 20,000 vpd 65,000 vpd 70,000 vpd 200,000 vpd vpd = vehicles per day Table 1. Comparison of enforcement benefits and costs at freeway work zones.
14 Work Zone Enforcement Deployment Procedures Safe work zones are the result of good planning and execu- tion. This is especially true with regard to the utilization of law enforcement. Simply hiring an off-duty officer or two and leaving them to figure out their role once they travel to the work zone is not sufficient to achieve the types of safety ben- efits desired. Rather, effective enforcement deployment and use in work zones requires cooperation and communication between highway agency, enforcement agency, and highway contractor personnel directly involved with the project. The following section describes a number of important proce- dures that should be followed as part of work zone enforce- ment deployment. The information pertains primarily to enforcement use in a traffic-calming role for particular work activities. However, some of the key items described, such as the officer making initial contact with the highway agency to discuss specific details about the project, are recommended for all types of enforcement use in work zones. Officer Arrival Procedures When officers are requested to be present for a particular work activity, it is desirable for the officer(s) providing that support to arrive at the work zone prior (15 minutes is some- times suggested) to the start of the activity. If it is the first time that the officer has been to the work zone, it is beneficial to drive up and down the roadway segment to become aware of such things as the locations of signs and channelizing devices, worker staging areas, ingress and egress points to the work zone and to the roadway facility, width, and continuity of shoulders across bridges, etc. After becoming familiarized with the project, the officer should contact the highway agency point-of-contact (POC) and the highway contractor POC. Cell phone numbers for the POCs should be provided to the officer as part of the request process so that this contact can be made. Specific details about the work activity that will impact where and how the officer is positioned within the work zone should be dis- cussed, including: ⢠Location Where The Temporary Traffic Control For The Work Activity Will Begin And End; ⢠Number Of Lanes (If Any) That Will Be Closed; ⢠Anticipated Start Time And Duration Of The Work Activity; ⢠Safest And Most Effective Location For Enforcement To Be Located; ⢠Where And How Many Construction Vehicles Will Be Entering And Exiting The Work Area, And Where The Entry And Exit Points Will Occur; ⢠Whether Traffic Congestion Is Expected To Develop, And How Far Upstream It Is Expected To Extend; ⢠Any Other Traffic Concerns That The POCs Have Based On Previous Or Current Conditions At The Site; ⢠Any Changes In Traffic Control That Might Occur During The Shift; And ⢠Exchange Of Cell Phone Numbers Or Other Means Of Contact Between The Officer And POCs, In Case The Need Arises To Contact Each Other During The Shift. It must be remembered that the lanes that are closed and the lane closure start and end points may change over the course of a work shift. In these cases, keeping the officer aware of the surrounding work activities would be very important. It may be necessary to notify the officer when changes to the traffic control layout occur so as to avoid putting the officer into an unsafe situation. As part of the initial meeting, the officer should verify which of the POCs (if more than one) has the authority to request a change in what the officer is doing. Situations can arise in which the priorities of the highway agency and highway contractor POCs relative to the use of enforcement are not the same, so authority for work zone decisions should be clarified in advance. Officer Deployment Within the Work Zone The determination of where the officer should be posi- tioned during a work activity should be discussed prior to each work shift. Figures 7 through 12 illustrate some typical officer deployments. These illustrations are taken from the 2009 Manual on Uniform Traffic Control Devices (MUTCD) (13), modified to show recommended locations of enforce- ment for various work zone conditions. Table 2 and Table 3 also come from the MUTCD. The safety of both the officer and the motoring public is the top priority in determining the appropriate enforcement location. When the enforcement vehicles are stationary or moving at low speeds (i.e., 20 mph or more below the normal speed of traffic), they should generally be located on the shoulder, in a closed travel lane beyond the buffer area of a merging taper, or protected by a shadow vehicle (preferably with a truck-mounted attenua- tor). Ideally, the enforcement vehicle will also be positioned such that motorists have adequate time to detect and react to the presence of enforcement prior to making path changes required by the work zone. Enforcement presence does attract significant motorist attention, and it is desirable that such attention not overload the driverâs ability to react safely to the established temporary traffic control for the work zone. It is also desirable that the enforcement vehicle be located on the same side of the roadway as the work area, although this may not be possible when the work area is located in a median lane and no median shoulder exists.
15 Figure 7. Suggested stationary enforcement position for lane closure when work activity area is less than 1 mile from the merging taper. These figures should be considered guides because site- specific factors such as shoulder widths, overpasses, work area access points, etc., can all influence the positioning of the enforcement vehicle. In some work zones, the appropri- ate location for enforcement may change over the course of a work shift as traffic conditions change. For example, traffic queuing that develops once a lane closure is installed may necessitate that the officer be positioned upstream of the work zone beyond the expected limits of the queue with lights flashing to warn approaching motorists. The officer may then adjust position as the queue grows or dissipates. At some time during the work shift, traffic volumes may drop to the point where queuing no longer occurs. At that time, the POCs may contact the officer and request a repositioning within the closed lane just upstream of the work activity area. If the officer has deployed to the desired location to func- tion in a traffic-calming role, a number of additional items should be checked and monitored: ⢠The vehicle should be as visible as possible, with emer- gency lights flashing (however, the headlights of the vehicle should be off),
16 ⢠If the officer is located outside of the vehicle to function as a police traffic controller, appropriate ANSI-approved safety apparel must be worn, and ⢠The condition of traffic flow should be monitored, and the POCs notified if problems develop. Obviously, these items would not necessarily apply when active enforcement was being used in or around the work zone. If a circulating patrol strategy is being utilized, officers should also be vigilant for any problems with the temporary traffic control set-up (i.e., arrow panel or portable changeable message sign quits working, signs or channelizing devices are knocked down, etc.), and should report those problems to the highway agency and/or contractor POCs as quickly as possible. Officer Departure Procedures At the conclusion of each work shift, the POCs and the officer should again meet briefly to discuss any issues that arose. In addition, many agencies require specific documen- tation to be completed verifying the following: ⢠The presence of the officer [name(s) and/or badge number(s)]; ⢠Hours worked; ⢠Type of enforcement support provided; and ⢠Whether any traffic crashes occurred that were witnessed by the officer. If the purpose of providing an officer was for actual traf- fic law enforcement purposes, the enforcement agency may want to record the number of stops made, and the number of tickets written by type of traffic violation that occurred as a way to track officer productivity. Often, the highway agency or highway contractor POC will need to sign the documentation to verify its accuracy. This documentation should occur away from the edge of the travel lanes, if possible, to minimize risks. Figure 8. Suggested stationary enforcement position at lane closure when work activity area is more than 1 mile from merging taper.
17 Figure 9. Suggested enforcement positioning in mobile operation convoy when continuous shoulder is available for travel.
18 Figure 10. Suggested enforcement positioning in mobile operation convoy in left lane when a continuous right shoulder is available for travel.
19 Figure 11. Suggested enforcement positioning in mobile operation convoy when no continuous shoulder is available for travel.
20 Figure 12. Suggested stationary enforcement position at alternating one-lane operations.
21 Road Type Distance Between Signs** A B C Urban (low speed)* Urban (high speed)* Rural Expressway / Freeway 100 feet 350 feet 500 feet 1,000 feet 100 feet 350 feet 500 feet 1,500 feet 100 feet 350 feet 500 feet 2,640 feet * Speed category to be determined by the highway agency ** The column headings A, B, and C are the dimensions shown in Figure 7 through Figure 12. The A dimension is the distance from the transition or point of restriction to the first sign. The B dimension is the distance between the first and second signs. The C dimension is the distance between the second and third signs. (The "first sign" is the sign in a three-sign series that is closest to the TTC [Temporary Traffic Control] zone. The "third sign" is the sign that is furthest upstream from the TTC zone.) Table 3. Advance warning sign spacing (13). Symbols Description Arrow board Arrow board support or trailer (shown facing down) Changeable message sign or support trailer Channelizing device Crash cushion Direction of traffic Flagger Shadow vehicle Sign (shown facing left) Police vehicle Truck-mounted attenuator Work space Work vehicle Table 2. Symbols used in typical enforcement applications (adapted from 13).
