Strategies for Improving Safety at Toll Collection Facilities

REDUCING UNSAFE MERGING AND LANE CHANGING

THE CHALLENGE

Toll plazas present unique challenges in terms of lane-changing behavior and merging. Many plazas operate much like a complex intersection (i.e., there are on-ramps or off-ramps in close proximity to the plaza creating excessive weaving maneuvers). In addition, speed variance between ETC and cash-paying customers is a safety challenge faced by all agencies with plazas accepting both electronic and cash payment. Often last minute lane changes occur simply because motorists are seeking out the shortest line - motorists commit to a toll lane in advance of the plaza but then see a shorter line at the plaza and switch lanes. Additionally, many agencies face challenges in dealing with truck traffic and over-sized loads, particularly in regard to their "mixing" with automobiles.

POTENTIAL MITIGATION STRATEGIES

Plaza Configuration

Toll authorities across the country have tackled the challenge of lane changing in a variety of ways. Many agencies make it a standard practice to position their dedicated high-speed ETC lanes to the left side of their plazas (i.e., toward the center of the roadway), with the idea that the customer expects faster-moving traffic to primarily be to the left side of the roadway. This practice appears to be effective except in situations where there are on-ramps or off-ramps in close proximity to the plaza, in which case positioning the ETC lanes to the left side of the plaza can cause unnecessary weaving maneuvers. To reduce weaving in these situations, some agencies have taken to positioning dedicated-ETC lanes to both the left and right side of their plazas as shown in Figure 19.

Figure 19. Dedicated ETC Lanes Positioned at Both Sides of a Plaza

Another strategy that some agencies feel works well is to keep the dedicated ETC lanes in the same location at plazas even if those plazas are reconfigured throughout the day as traffic density changes. This assists ETC patrons with identifying the proper lane and knowing that it is always in the same place. Another agency reported that when reconfiguring its plaza to include dedicated ETC lanes whereas previously cash and ETC were accepted in all lanes, it reviewed ETC usage in all lanes to determine which lane(s) would be best for dedicated-ETC. Previously, cash and ETC were accepted in all lanes.

Safety can be further compromised when truck traffic which normally travels in right lanes seeks out ETC lanes. A common issue is that trucks are prohibited from traveling in the left lane on many roadways, which can pose a weaving problem if the dedicated-ETC lanes and/or the truck-only lanes are located to the left side of the plaza. To address this concern, the Illinois Toll Authority solicited feedback from truck drivers on the best configuration for its truck lanes. The agency recruited a number of commercial truck drivers and asked them to drive the agency's facility and indicate where the truckers would ideally like to access the plaza. Truck-only lanes were then situated based in part on these responses.

Channelization of Traffic

One way to reduce last-minute lane changes is to channelize traffic well in advance of the plaza to reduce last-minute lane changes (as shown in Figure 20). Similarly, some agencies channelize ETC traffic downstream of the plaza to delay the merging of traffic (as shown in Figure 21). Some agencies even make it a policy to separate traffic until the slower traffic has accelerated to two-thirds of the normal operating speed.

Figure 20. Concrete Barriers and Attenuators Physically Separate Traffic Upstream of an Illinois Tollway Plaza

Other agencies use a buffer lane between the ETC lanes and cash or mixed-use lanes. Others use physical separation (such as a concrete barrier), including the use of barriers to prevent vehicles in the left-most (ETC) lanes from making unsafe maneuvers to reach off-ramps located just downstream of the plaza. However, physical barriers can be costly to install and costly to maintain. As a result, some agencies simply extend the longitudinal markings further upstream of the toll plaza to assist with lane delineation. Others use high-visibility flexible delineators to separate traffic at plazas. The Florida Turnpike has found it effective to use wide yellow sergeant-striped delineators in place of the solid white delineators that it previously used to separate traffic. The agency also found that visibility was improved after positioning the delineators in a "bowling pin" configuration instead of in a straight line.

Figure 21. Pavement Markings and Cones Delay Merging Downstream at the Port Authority of NY & NJ's Holland Tunnel Plaza

For those agencies that face the additional challenge of lane assignments changing throughout the day, pop-up delineators can be a solution. However, some agencies in colder climates have found that pop-up delineators do not perform so well during snowy and icy conditions. To address this, the NYS Thruway designed a new pop-up delineator in-house that operates off of air compression and survives the winters.

Strategy Rankings, Effectiveness, and Constraints

Table 5 lists each strategy identified for mitigating safety issues associated with merging and lane-changing behavior and provides comments from practitioners on strategy effectiveness and any concerns/constraints. The table also provides information on practitioner ranking results from the Toll Facility Safety Study Workshop.

Table 5. Potential Strategies to Mitigate Safety Issues Associated with Merging and Lane-Changing Behavior

Strategy	Description	Rankings from Workshop Participants and Comments on Effectiveness13	Concerns / Constraints
Plaza Configuration
Position ETC lanes on both the right and the left side of plazas with nearby on or off ramps.	In situations where a plaza is quickly followed by an off-ramp, it can be dangerous for high-speed ETC traffic to have to quickly weave across multiple lanes of traffic to utilize the ramp. This is exacerbated in areas with high percentages of truck traffic.	Seven of 20 workshop participants selected this solution as a top three strategy. Six of those 7 participants selected it as the second most effective solution. There is considerable debate about this practice. While most consider that the practice will increase driver safety there are concerns that it can decrease worker safety - forcing collectors to cross high-speed lanes to reach staffed booths.	In many locations the practice is prevented by physical constraints. Can lead to increased worker exposure to high-speed lanes. Concerns that it may be confusing to drivers. Requires additional signs. Additional ETC lane may be blocked by queues from cash lanes. Could create additional, unexpected weaving problems.
Select location of truck-only lanes at plaza based on feedback from truck drivers.	A number of agencies face difficulties with trucks having to merge from shoulder travel lanes to median lanes to access ETC and then merging back across traffic. To address this concern, the Illinois Toll Authority recruited a number of commercial truck drivers and asked them to drive the agency's facility and indicate where they would ideally like to access the plaza. Truck-only lanes were then situated based in part on these responses.	Three of 20 workshop participants selected this solution as a top three strategy. While workshop participants felt that the practice of situating truck-only lanes based on user feedback was effective, there were concerns about the use of truck-only lanes in general.	The constraints identified referred to the general practice of truck-only lanes and centered around limited space to implement such an operation.
Channelization of Traffic
Channelize traffic downstream of the plaza with delineators.	While many facilities actively separate traffic upstream of the plazas, a smaller number make use of delineators (and to a lesser extent physical barriers) to similarly maintain separation for some length downstream of the plaza.	Eight of 20 workshop participants selected this solution as a top three strategy. None rated it as the most effective strategy, but five of the 8 participants selected it as the third most effective solution. Would be most effective if the delineated section extended far enough to allow vehicles from the cash and mixed lanes to accelerate to match the speeds of the ETC traffic.	Many plazas simply do not have the space. As with all delineators introduces worker safety issues associated with placement and maintenance.
Provide a buffer lane between ETC and cash customers.	A small number of agencies use buffer or unused lanes between ETC and cash or mixed lanes. As more and more customers move to ETC and fewer lanes are required at plazas, this is becoming more feasible.	Six of 20 workshop participants selected this solution as a top three strategy. Felt to be more economical than the use of physical barriers.	Many plazas simply do not have the space to support unused lanes. Violators may try to use the buffer lane in an attempt to bypass the toll. May confuse patrons. If used intermittently may create an unsafe situation for workers during buffer lane closing and opening.
Use physical barriers to separate approaching high-speed traffic from cash or mixed lanes.	A number of agencies use physical separation such as concrete barriers to separate high-speed ETC traffic from lower speed mixed or cash traffic. The length of separation and the type of barrier varies greatly among the facilities employing this technique.	Eighteen of 20 workshop participants selected this solution as a top three strategy. Fifteen of those 18 participants selected it as the most effective solution.	Barriers themselves could become safety hazards. Installation and maintenance costs are high. Customers may inadvertently become "trapped" in the wrong lane and try to back up. Implementation may be restricted by lane width considerations. May present challenges to snow removal.
Use physical barriers to prevent vehicles in left-most lane from making unsafe maneuvers to reach downstream off-ramps.	In situations where off-ramps are immediately downstream of a plaza, some authorities physically prevent vehicles in left-most lanes from merging across traffic to reach the off-ramp. Other authorities use striping and signs to try to enforce such restrictions; however, this was felt to be less effective than physical barriers.	Five of 20 workshop participants selected this solution as a top three strategy. Four of those 5 participants selected it as the third most effective solution. Felt to be effective only with physical barriers versus lane striping, barrels, cones, or delineators.	Concerns that it may confuse patrons and cause them to back up.
Use high-visibility flexible delineators to separate traffic lanes.	This method of separating traffic lanes makes use of physical delineators in the roadway that are less expensive to deploy and that do not provide the same physical separation as barriers. Over time agencies have evolved to increasingly higher visibility delineators such as wide sergeant stripe panels and arrangements of multiple delineators in bowling pin configurations.	Nine of 20 workshop participants selected this solution as a top three strategy. Three of those 9 participants selected it as the most effective solution. Considered more cost-effective to deploy than physical barriers.	Agencies reported a number of concerns, associated with maintenance of delineators including cost and worker safety.
Use pop-up delineators to reduce worker exposure at plazas requiring lane changes throughout the day.	Pop-up delineators are systems where the delineators reside in the pavement and can be automatically activated or raised to demark lanes or support lane closures.	Four of 20 workshop participants selected this solution as a top three strategy. Three of those 4 participants selected it as the second most effective solution. Those facilities that employed the technique, such as the NY State Thruway, were very pleased with their operation and felt that the use of the delineators helped to reduce the worker exposure that is necessitated by manual systems.	Some concerns about operation in areas with snow and ice. However, the NY State Thruway's compressed air system appears to have overcome this operational challenge. Felt to be an expensive solution that introduces its own maintenance concerns.

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¹³ Within this group of strategies, workshop participants were asked to select and rank the top three strategies that they believed to have the greatest potential to mitigate merging and lane-changing behavior.