Estimating Fatality and Injury Savings Because of Deployment of Advanced Wrong-Way Driving Countermeasures on a Toll Road Network

Abstract

Limited access facility wrong-way driving (WWD) crashes are typically more severe than other crashes. Deploying advanced WWD countermeasures, such as rectangular flashing beacon (RFB) and light-emitting diode (LED) technologies, at exit ramps can reduce WWD crashes, injuries, and fatalities. No previous research has developed a methodology to quantify the potential fatality and injury savings because of future countermeasure deployments. This paper developed such a methodology and applied it to Florida’s Turnpike Enterprise (FTE) toll road network. From 2011–2016, there were 53 FTE WWD crashes, resulting in 16 fatalities and annual injury costs of $37 million. The proportion of these crashes occurring during night-time was 87%. RFB and LED life-cycle injury savings and costs were determined for all 216 FTE exits. The total savings were $424 million for RFBs (benefit–cost [B/C] ratio of 23.20) and $144 million for LEDs (B/C ratio of 13.13). Deploying countermeasures at the 103 exits with the highest B/C ratios would provide 70% of the total possible savings by equipping 40% of the ramps. For the same capital investment, RFBs provide more savings than LEDs. Spending $1 million to deploy RFBs will provide similar savings as spending $3.4 million to deploy LEDs. Evaluating the existing FTE RFB and LED ramps shows that RFBs are more effective at night-time and can provide three times the savings of LEDs. The results of this paper show the improved performance of RFBs over LEDs and provide an example that other agencies could follow to identify savings and cost-effectively deploy advanced WWD countermeasures.

There are many factors that affect the severity of traffic crashes, with some types of crashes being more prone to serious injuries and fatalities than others. Freeway wrong-way driving (WWD) crashes are one of the most severe crash types, because of high travel speeds and typical head-on collisions. Studies have shown that fatality rates for WWD crashes can be 27 times higher than for other crashes ( 1 ). In the United States (U.S.), there were 33,654 fatal crashes with 36,560 fatalities in 2018 (fatality rate of 1.09 fatalities per fatal crash) ( 2 ). For WWD, a fatality rate of 1.34 fatalities per fatal WWD crash was determined using national data from 2004 to 2013 ( 3 ). This shows the increased severity of WWD crashes.

Florida is one state with a high number of fatal WWD crashes. Based on Fatality Analysis Reporting System (FARS) data from 2014 to 2018, 323 of the 5,596 fatal WWD crashes in the U.S. (5.8%) occurred in Florida, with only Texas and California having more fatal WWD crashes ( 2 ). To reduce these WWD crashes (especially on limited access facilities), agencies throughout Florida have implemented advanced Intelligent transportation systems (ITS) countermeasures. Florida’s Turnpike Enterprise (FTE) is one such agency. FTE operates nine toll roads containing 2,423 lane miles and 144 interchanges throughout Florida; these roadways are used by three million travelers daily ( 4 ). In October 2014, FTE installed “Wrong Way” signs with light-emitting diodes (LEDs) at 17 South Florida exit ramps to combat WWD (Figure 1a). “Wrong Way” signs with rectangular flashing beacons (RFBs) were installed in June 2017 at 18 Central Florida ramps to further combat WWD (Figure 1b) ( 5 ). The LED installations contain one pair of signs while the RFB installations contain two pairs of signs. A previous study of these devices showed that both have successfully reduced WWD, with the RFBs causing more detected wrong-way vehicles to turn around than the LEDs ( 6 ).

Figure 1.

Examples of wrong-way driving (WWD) countermeasure: (a) light-emitting diode (LED) and (b) rectangular flashing beacon (RFB) (5).

The success of these devices on the FTE system suggests that deployments by other agencies could provide similar benefits. However, their high costs could discourage agencies from deploying them. An optimization approach was previously used to identify exits where advanced countermeasure deployment would provide the most WWD crash risk (WWCR) reduction for the lowest cost ( 7 ). While this approach identified the best deployment locations and estimated WWCR reductions, it did not quantify the monetary benefits because of these countermeasures. Converting turnaround percentages and WWCR reductions into fatality and injury savings (which are collectively referred to as injury savings in the remainder of this paper) will more clearly illustrate the impacts and value of these countermeasures.

In this paper, a methodology is developed to determine and compare the economic performance of RFB and LED WWD countermeasures. This methodology is applied to the FTE system, but other agencies could use it to determine WWD countermeasure savings for their systems. Life-cycle benefit–cost (B/C) ratios are determined for all FTE exit ramps with and without advanced WWD countermeasures separately. These B/C ratios are based on injury savings, deployment costs, and operations and maintenance (O&M) costs for the installation setups used by FTE. Other agencies could experience different costs and savings for different setups, such as the use of additional LED signs. B/C ratios for RFB and LEDs are compared for different scenarios to show the advantages and disadvantages of each countermeasure. These scenarios include deployments at all exits without these devices, select deployments based on B/C ratio rankings and capital investment levels, and evaluations of existing RFB and LED deployments. Injury savings because of WWD countermeasure deployments at individual exits have never been estimated before. Additionally, RFBs and LEDs deployed on the same system have never been evaluated with the detailed comparisons and quantity of data used in this paper. By showing the quantitative benefits of RFB and LED WWD countermeasures, this paper can help agencies better understand their potential and effectiveness in reducing WWD.

Literature Review

Many states have analyzed WWD crashes and found that they are more severe and result in more fatalities than other types of limited access crashes. In North Carolina, WWD crashes from 2000 to 2005 accounted for 0.2% of freeway crashes, but had 5.6% of freeway fatalities ( 8 ). A study in Texas found that about 20% of freeway WWD crashes from 1997 to 2000 were fatal and that all 323 freeway WWD crashes during this period had an economic impact of about $21 million per year ( 9 ). Analysis of Texas WWD crash data from 2007 to 2011 found that freeway WWD crashes were 0.07% of all crashes, but 1% of all fatal crashes ( 10 ). Examination of WWD crash data on Florida limited access facilities found that there were 280 WWD crashes from 2009 to 2013, with 18% being fatal ( 11 ). In Arizona, it was found that 1% of all divided highway crashes from 2004 to 2014 were fatal, compared with 25% of WWD crashes ( 12 ). WWD fatal crashes also had a higher fatality rate (1.5 fatalities per fatal crash) than all fatal crashes (1.1 fatalities per fatal crash) ( 12 ). Examination of freeway WWD crashes in Illinois from 2004 to 2009 found that there were 44 fatalities from 31 fatal crashes (1.4 fatalities per fatal crash) and estimated total economic impacts of $67.8 million ( 13 ). Studies of WWD crashes in Louisiana and Kansas also found that a higher percentage of WWD crashes resulted in fatalities or serious injuries than other types of crashes ( 14 , 15 ).

To reduce WWD and its associated fatalities, agencies throughout the U.S. have deployed various WWD countermeasures. These include preventative countermeasures (such as enhanced signs and geometric modifications) designed to stop drivers from entering freeways the wrong way, and reactive countermeasures (such as advanced ITS countermeasures with detection and alerting capabilities) designed to stop wrong-way drivers from continuing, thereby reducing the chance of crashes ( 16 ). Since most advanced countermeasure deployments have occurred within the last 5 years, there are limited studies on their effectiveness. A study in Florida by the authors of this paper found that RFBs on Central Florida Expressway Authority (CFX) toll roads have caused over 83% of detected wrong-way vehicles to turn around and could provide between $26.5 and $40 million in injury savings over their 10-year life cycle ( 17 ). Other Florida studies on rectangular rapid flashing beacons (RRFBs) in Tampa and RFBs on FTE ramps found similar turnaround results ( 6 , 7 , 18 ). Studies of Florida LED WWD countermeasures found that they have much lower turnaround percentages than RFBs, but can reduce WWD 911 calls and citations by up to 48% ( 5 , 6 ). Combined, Florida RFB and LED WWD countermeasures were estimated to have saved law enforcement officers over 116 h by confirming when detected wrong-way vehicles turn around ( 19 ). In Texas, analysis of LED WWD countermeasures installed on US 281 found a 30% reduction in WWD, resulting in an estimated B/C ratio of 13:1 for a 20-year life cycle ( 20 ).

This literature review shows that few studies have examined the economic impacts of WWD and the savings that can be provided by advanced WWD countermeasures. Additionally, no studies have considered the potential savings because of future deployments, but only examined existing deployments. This paper will estimate these future savings because of LED and RFB countermeasures for the FTE system. Previous efforts by the authors show the ability of the developed WWCR modeling and optimization approach to accurately identify limited access segments with high WWCR and predict WWCR reductions for individual exits (7, 21–25). By incorporating injury costs for WWD crashes, this approach can be used to determine the life-cycle benefits of advanced WWD countermeasure deployments, calculate B/C ratios for individual exits, and compare RFB and LED countermeasures.

Research Goal and Objectives

The goal of this paper is to develop a methodology that agencies can use to identify the financial impacts of WWD and the savings that can be provided by advanced countermeasures. The objectives of this methodology are to determine the severity distribution and injury costs of WWD crashes, estimate life-cycle WWCR reductions and injury savings that could be achieved by deploying advanced countermeasures, compare the economic performance of different countermeasures, identify B/C ratios for individual exits, and evaluate currently installed advanced WWD countermeasures. An example application of this methodology involving RFB and LED countermeasures on the FTE toll road network system is used to illustrate its procedures.

Research Methodology

This paper’s research methodology consists of the six steps shown in Figure 2 (detailed in this section). By following these steps, agencies can thoroughly understand the impacts of WWD and advanced countermeasures on their system and select the best type and quantity of devices for future deployments. Step 6 is not needed for agencies which do not currently have any advanced WWD countermeasures on their roadways. While these steps are applied to RFB and LED countermeasures in this paper, they could also be applied to other types of WWD countermeasures.

Figure 2.

Methodology steps to determine injury savings and economic performance of future and existing advanced wrong-way driving (WWD) countermeasure deployments.

The first step is collecting and analyzing WWD crash data. This analysis shows the severity and financial impacts of WWD crashes, as well as common features that should be addressed by any deployed countermeasures (such as time periods when WWD crashes are more frequent). The average injury cost per WWD crash can be calculated using Equation 1.

Average Injury Cost per WWD Crash = \sum_{s = 1}^{S} (I R_{s}) (C_{s})

(1)

where $I R_{s} =$ injury rate for severity level $s$ ;

$C_{s} =$ injury cost per crash for severity level $s$ ; and

$S =$ number of severity levels.

The next step is to determine the advanced WWD countermeasures that will be studied. One or more types of countermeasures can be considered and compared using this methodology. Capital costs, annual O&M costs, effectiveness measures, and expected lifespans need to be obtained for these countermeasures. Equations 2 and 3 can be used to convert annual values into present values and present values into future values, respectively.

PV = AV \times [\frac{1 - {(1 + i)}^{- n}}{i}]

(2)

FV = PV \times {(1 + i)}^{n}

(3)

where $PV =$ present value;

$AV =$ annual value;

$i =$ interest rate;

$n =$ number of years; and

$FV =$ future value.

In step 3, WWCR reductions because of deployment of advanced WWD countermeasures are calculated for each countermeasure type at each exit using Equation 4.

WWC R_{j, c} = \sum_{k} (WWC R_{k}) (E_{j, k}) (P_{c}) (\frac{n}{n_{j}}), j \in k

(4)

where $WWC R_{j, c} =$ WWCR reduction because of deploying countermeasures of type $c$ at exit $j$ ;

$WWC R_{k} =$ WWCR for multi-exit roadway segment $k$ ;

$E_{j, k} =$ proportion of WWD entry value in segment $k$ provided by exit $j$ ;

$P_{c} =$ effectiveness of advanced WWD countermeasure of type $c$ ( $c = 1 to n_{c})$ ;

$n_{c} =$ number of countermeasure types considered;

$n =$ number of exits in each segment; and

$n_{j} =$ number of segments that contain exit $j$ (1 ≤ $n_{j}$ ≤ $n$ ).

In Equation 4, it is assumed that countermeasures are installed at all ramps at an exit, since it is unknown which ramp will experience more WWD at exits with multiple ramps. The $WWC R_{k}$ values can be determined using the WWCR segment modeling methodology discussed by Sandt and Al-Deek ( 7 ). Adding the predicted values from the model to the actual number of crashes in each segment provides a $WWC R_{k}$ value for each segment. Equation 5 shows the model developed for the FTE system, which predicts the number of WWD crashes on six-exit segments for a 5-year period. This model will vary for each agency based on its WWD event data and interchange characteristics. After obtaining $WWC R_{j, c}$ values, they need to be divided by $n_{j}$ and the number of years of data included in the WWCR model to obtain average annual WWCR reduction values. Multiplying these values by the expected lifespan of the countermeasure will provide life-cycle WWCR reduction values ( $WWC R_{LC, j, c})$ .

\begin{matrix} \ln (WWD Crashes) = - 0.472 - 0.094 (WWD Citations) \\ + 0.046 (WWD 911 Calls) \\ + 0.175 (Number of Partial Diamond Exits) \\ - 0.145 (Number of Three - Leg Exits) \\ + 0.358 (Number of Service Plazas) \end{matrix}

(5)

$E_{j, k}$ in Equation 4 is determined by distributing WWD events to the nearest possible entry points based on the number of exits typically traveled, resulting in a WWD entry value for each exit. An exit’s WWD entry value is then divided by the segment WWD entry value for all segments that contain the exit. $P_{c}$ represents how much WWCR reduction is provided by the countermeasure. Common effectiveness measures include turnaround percentages and reductions in WWD 911 calls, citations, or both. The last component in Equation 4 is a weighting factor that adjusts the WWCR for exits at the end of roadways which are in fewer than n segments.

For step 4 of the methodology, life-cycle injury savings benefits and costs are calculated for each exit that does not currently have advanced WWD countermeasures, using Equations 6 and 7. Equations 2 and 3 need to be used so the benefits and costs have the same present year. $I C_{LC}$ is determined by using the average injury cost per WWD crash (Equation 1) as an annual value for the entire life cycle, converting to a present value, and dividing by the length of the life cycle. $D C_{LC, c}$ includes capital costs and O&M costs converted to a present value. Dividing the benefits by the costs provides life-cycle B/C ratios for each exit. Ranking exits by their B/C ratios shows which exits provide the most cost-effective benefits, and can be used to develop various benefit and cost curves and heat maps showing priority deployment locations. Since the costs depend on the number of ramps at the exit, an exit with two ramps will require double the benefits of an exit with one ramp to have the same B/C ratio. Comparing the percentage of the total benefits (if countermeasures were deployed at all exits) with the percentage of total costs (if countermeasures were deployed at all exits) for each exit can show the economically ideal number of exits (percent benefits greater than percent costs). Benefits and costs for different countermeasures can also be compared.

B_{j} = (WWC R_{LC, j, c}) (I C_{LC})

(6)

C_{j} = (r_{j}) (D C_{LC, c})

(7)

where $B_{j} =$ life-cycle injury savings benefits for exit $j$ ;

$I C_{LC} =$ life-cycle average injury cost per WWD crash;

$C_{j} =$ life-cycle costs for exit $j$ ;

$r_{j} =$ number of exit ramps at exit $j$ ; and

$D C_{LC, c} =$ life-cycle deployment costs of type $c$ advanced WWD countermeasure per ramp.

Next, various scenarios can be investigated to see the savings for different capital investment levels and different countermeasures. These scenarios can show whether a countermeasure with high effectiveness and costs provides more savings than one with lower effectiveness and costs for the same capital investment. The final step of the methodology is evaluating existing sites with advanced WWD countermeasures. Benefits and costs can be calculated for these sites using the procedures in this methodology. These can be used to identify savings provided by these existing devices for the life cycle and current implementation period and compare between different deployments. Other important characteristics identified in step 1 can also be considered in these evaluations.

Application of Methodology to FTE System

To demonstrate this methodology and its procedures, it is was applied to the FTE system. Each step of the methodology is discussed in its own subsection

Analysis of FTE and Florida Limited Access WWD Crashes

Six years (2011–2016) of WWD crash data provided by FTE were analyzed for the FTE system and other Florida limited access facilities. Complete crash data after 2016 were not available at the time of writing this paper. There were 53 WWD crashes on the FTE system from 2011 to 2016, including 13 fatal crashes resulting in 16 fatalities (1.23 fatalities per fatal WWD crash). Figure 3 shows the number of WWD crashes by severity level (fatal, incapacitating injury, non-incapacitating injury, possible injury, and no injury or property damage only [PDO]) for four different time periods. About 87% of the FTE WWD crashes occurred from 6:00 p.m. to 5:59 a.m. (mainly night-time), including 11 of the 13 fatal crashes, with 58% occurring from midnight to 5:59 a.m. The high frequency of WWD crashes at night shows that any implemented countermeasures need to be especially effective during night-time hours. Thirty of the 53 crashes (56.6%) were definitely or likely caused by intoxicated drivers, with 29 of these 30 crashes occurring between 6:00 p.m. and 5:59 a.m. The average age of the wrong-way drivers in these crashes was 39.4 (median age of 34.0), with more crashes caused by drivers aged 25 or younger (22.6%) than drivers aged 65 or older (11.3%).

Figure 3.

Florida’s Turnpike Enterprise (FTE) wrong-way driving (WWD) crashes by severity level and time of day.

Tables 1 and 2 show the severity distribution and injury rates of WWD crashes for FTE roadways and all Florida limited access facilities, respectively. The comprehensive crash costs were obtained from the Florida Department of Transportation (FDOT) design manual and the injury costs were obtained from the National Safety Council ( 26 , 27 ). Reported property damage values from the WWD crash reports were used to determine the comprehensive crash cost of $17,881 for PDO crashes rather than using the recommended value of $7,600 ( 26 ). Values in parentheses in the second column of both tables indicate the percentage of the total WWD crashes in each severity level. The total crash and injury costs were obtained by multiplying the costs for each severity level by the number of crashes or injuries in that severity level.

Table 1.

Severity of Florida’s Turnpike Enterprise (FTE) Wrong-Way Driving (WWD) Crashes (2011–2016)

Severity	FTE WWD crashes (2011–2016)	Comprehensive crash cost per FTE WWD crash	Number of injuries	Injury rate per WWD crash	Injury cost
Fatal	13 (24.5%)	$10,560,000	16	0.30	$10,855,000
Incapacitating injury	10 (18.9%)	$599,040	26	0.49	$1,187,000
Non-incapacitating injury	9 (17.0%)	$162,240	27	0.51	$327,000
Possible injury	3 (5.6%)	$100,800	14	0.26	$151,000
Property damage only	18 (34.0%)	$17,881	97	1.83	$50,000
Total	53	$145,354,824	180	3.39	$220,335,000

Table 2.

Severity of Florida Limited Access Wrong-Way Driving (WWD) Crashes (2011–2016)

Severity	Florida limited access WWD crashes (2011–2016)	Comprehensive crash cost per Florida limited access WWD crash	Number of injuries	Injury rate per WWD crash	Injury cost
Fatal	73 (23.2%)	$10,560,000	110	0.35	$10,855,000
Incapacitating injury	52 (16.5%)	$599,040	148	0.47	$1,187,000
Non-incapacitating injury	69 (21.9%)	$162,240	182	0.58	$327,000
Possible injury	38 (12.1%)	$100,800	170	0.54	$151,000
Property damage only	83 (26.3%)	$17,881	447	1.42	$50,000
Total	315	$818,539,189	1,057	3.36	$1,477,260,000

The 53 FTE crashes had an estimated comprehensive crash cost of $145 million and an estimated injury cost of $220 million (annual costs of approximately $24 million and $37 million). The higher injury costs are because of the higher fatality rate for WWD crashes compared with other crashes, indicating that crash costs for other crash types might not be representative of the cost of WWD crashes. Therefore, injury savings are considered in the remainder of this paper rather than crash savings since injury savings account for the higher fatality rate of WWD crashes. These values show that even reducing WWD by a small amount can provide significant benefits. For all Florida limited access facilities, the fatality rate was 1.51 fatalities per fatal WWD crash, which is higher than the national average reported in ( 3 ). Using Equation 1 and the data in Table 2, the average injury cost was $4,689,714 per WWD crash.

FTE Advanced WWD Countermeasures

FTE has already deployed RFB and LED countermeasures at 35 exit ramps on their system, so both these countermeasures were considered for future deployments. These countermeasures have expected lifespans of 10 years. Data from existing sites through February 2020 were used to determine their effectiveness and costs with turnaround percentages used to represent their effectiveness ( $P_{c}$ in Equation 4). These percentages were 46/65 = 70.8% for the RFBs and 26/122 = 21.3% for the LEDs. Some of these detected wrong-way vehicles might have turned around without the RFBs or LEDs, but it is unknown what the turnaround percentages are for ramps without the countermeasures because of a lack of WWD detection and monitoring equipment at ramps without advanced countermeasures. The present values of the capital and O&M costs were $60,132 per ramp for the RFBs (in 2017$) and $32,001 per ramp for the LEDs (in 2014$) using a 10-year life cycle and 4% interest rate as recommended by FDOT for both countermeasures ( 26 ). 2020 was used as the present year when examining the 216 FTE exits which currently do not have these countermeasures, while 2017 was used as the present year when examining the existing RFB and LED sites. Therefore, the RFB costs are $60,132 (2017$) and $67,640 (2020$) and the LED costs are $35,997 (2017$) and $40,492 (2020$).

Life-Cycle WWCR Reductions for FTE Exits Currently Without RFBs or LEDs

Equation 4 was used to calculate WWCR reductions because of RFBs and LEDs for all 216 FTE exits (270 ramps) without these countermeasures. Segment WWCR values were determined using the WWCR model shown in Equation 5. The $E_{j, k}$ values were determined using the distribution of the number of exits traveled by wrong-way vehicles discussed by Sandt and Al-Deek to calculate WWD entry values for each exit and segment ( 7 ). The calculated $WWC R_{j, c}$ values were divided by six (since each roadway segment had six exits) and multiplied by two (since they represent 5-year values and the life cycle is 10 years) to obtain $WWC R_{LC, j, c}$ values for RFBs and LEDs at each exit.

Life-Cycle RFB and LED B/C Ratios for FTE Exits Currently Without These Countermeasures

The calculated injury costs and WWCR reductions were used to determine life-cycle injury savings for each exit (Equation 6). Using the average injury cost of $4,689,714 per WWD crash resulted in $I C_{LC} =$ $3,803,778 per life-cycle WWD crash in 2020$. Life-cycle costs were determined for each exit using Equation 7 and the countermeasure costs previously discussed. Life-cycle RFB and LED B/C ratios were then determined for all 216 FTE exits and used to rank them, with a ranking of 1 indicating the highest B/C ratio. Figures 4 –6 show the injury savings, costs, and B/C ratios, respectively, for each exit ordered by their B/C ratio ranking. RFB values are shown in blue and LED values are shown in orange. The peaks in these figures indicate exits with multiple exit ramps. Since it was assumed that countermeasures will be equipped on all ramps at an exit and countermeasure costs were on a per-ramp basis, exits with multiple ramps have higher costs. Therefore, these exits provide more savings than some prior exits with only one exit ramp (savings calculated per exit, not per ramp), but their higher costs mean their B/C ratios are lower than all prior exits.

Figure 4.

Rectangular flashing beacon (RFB) and light-emitting diode (LED) life-cycle injury savings benefits for exits without these countermeasures.

Figure 5.

Rectangular flashing beacon (RFB) and light-emitting diode (LED) life-cycle costs for exits without these countermeasures.

Figure 6.

Rectangular flashing beacon (RFB) and light-emitting diode (LED) life-cycle benefit–cost (B/C) ratios for exits without these countermeasures.

The figures show that the RFBs provide substantially more savings and have higher B/C ratios than the LEDs, even though they have higher costs. This is because of the better effectiveness of the RFBs (70.8% turnarounds) compared with the LEDs (21.3% turnarounds). The highest exit B/C ratio was 94.51 with RFBs and 53.48 with LEDs. Deploying RFBs at all 216 exits is expected to provide a life-cycle WWCR reduction of 99 (prevent 99 potential WWD crashes) with $423,755,288 in life-cycle injury savings for a total life-cycle cost of $18,262,881 (total B/C ratio of 23.20). Compared with the RFBs, deploying LEDs at all 216 exits is only expected to provide a life-cycle WWCR reduction of 30 with $143,543,718 in life-cycle injury savings for a total life-cycle cost of $10,932,802 (total B/C ratio of 13.13). These results show that the RFBs will provide about three times the savings of the LEDs for less than twice the cost.

Figures 7 and 8 show the cumulative RFB and LED benefits and costs, respectively, as exits are equipped in the order of their B/C ratio rankings. The benefit curves flatten out as more exits are equipped, with occasional jumps as exits with multiple ramps are equipped. Conversely, the cost curves have generally stable slopes, with increases at the end as the high-cost, low-WWCR exits are equipped. These figures suggest that it is not economical to deploy advanced WWD countermeasures at all exits. Comparing the percentage of the total benefits provided by each exit with its percentage of the total cost (as discussed in the methodology) indicates the ideal number of exits to equip with countermeasures. Figure 9 shows the percent benefits divided by the percent costs for each exit in order of B/C ratio ranking. These values are the same for the RFBs and the LEDs since they are percentages and not absolute values. The percent benefits exceed the percent costs (quotient is greater than 1.00) for the first 103 exits, suggesting these are the ideal exits for deployment. Even though the life-cycle B/C ratios for most of the last 113 exits are above 1.00, they only provide a small portion of the total benefits compared with their costs.

Figure 7.

Cumulative rectangular flashing beacon (RFB) and light-emitting diode (LED) life-cycle injury savings for exits without these countermeasures.

Figure 8.

Cumulative rectangular flashing beacon (RFB) and light-emitting diode (LED) life-cycle costs for exits without these countermeasures.

Figure 9.

Percentage of total life-cycle benefits divided by percentage of total life-cycle costs per exit for exits without these countermeasures.

Table 3 shows the benefits and costs for these 103 ideal exits compared with all 216 FTE exits currently without RFBs or LEDs. Values in parentheses indicate percentages of the totals for all exits. These 103 exits provide almost 70% of the total possible WWCR reduction, even though they only contain 40% of the total ramps. Deploying RFBs at these ramps will provide over $295 million in life-cycle injury savings for a life-cycle cost of $7.4 million (B/C ratio of 40.12). Equipping these ramps with LEDs is only expected to provide $100 million in life-cycle injury savings for a cost of $4.4 million (B/C ratio of 22.70). Over three times more crashes could potentially be prevented with RFBs compared with LEDs.

Table 3.

Benefits and Costs of Deploying Rectangular Flashing Beacons (RFBs) and Light-Emitting Diodes (LEDs) at 103 Ideal Florida’s Turnpike Enterprise (FTE) Exits and All FTE Exits Without Advanced Wrong-Way Driving (WWD) Countermeasures

Parameter	RFBs (all exits)	RFBs (ideal exits)	LEDs (all exits)	LEDs (ideal exits)
Number of exits	216	103 (47.7%)	216	103 (47.7%)
Number of ramps	270	109 (40.4%)	270	109 (40.4%)
Life-cycle wrong-way driving crash risk reduction	99.04	69.13 (69.8%)	29.82	20.82 (69.8%)
Life-cycle injury savings benefits (2020$)	$423,755,288	$295,768,122	$143,543,718	$100,189,088
Life-cycle costs (2020$)	$18,262,881	$7,372,793	$10,932,802	$4,413,613
Life-cycle benefit–cost ratio	23.20	40.12	13.13	22.70

Investigating RFB and LED Benefits and Costs for Different Capital Investment Levels

While the savings provided by the RFBs and LEDs can be substantial, their high costs and limited availability of resources make it impractical to deploy them at many sites. Since the LEDs cost less than the RFBs, they can be deployed at more locations for the same investment. Comparing the benefits of both countermeasures for the same capital investment will show whether the improved performance of the RFBs outweighs the extra benefits provided by the additional LED sites.

Table 4 shows the benefits and costs of RFB and LED deployment at the FTE exits with the highest B/C ratios for capital investment levels of $1 million and $2 million. Values in parentheses indicate percentages of the totals for all 216 FTE exits (shown in Table 3). The RFBs provide over twice as much life-cycle injury savings as the LEDs, even though they are equipped at less exits. LEDs would have to be deployed at the 132 exits (145 ramps) with the highest B/C ratios (capital investment of $3,371,284) to achieve the same savings as the RFBs do for a $1 million investment. The RFB savings for a $2 million investment are higher than the maximum savings for LEDs if they were equipped at all 216 exits. These comparisons show the improved performance and cost-effectiveness of the RFBs over the LEDs.

Table 4.

Benefits and Costs of Deploying Rectangular Flashing Beacons (RFBs) and Light-Emitting Diodes (LEDs) at Florida’s Turnpike Enterprise Exits for Capital Investments of $1 Million and $2 Million

Parameter	Capital investment of $1 million (2020$)		Capital investment of $2 million (2020$)
Parameter	RFBs	LEDs	RFBs	LEDs
Number of exits	26 (12.0%)	40 (18.5%)	53 (24.5%)	82 (38.0%)
Number of ramps	28 (10.4%)	43 (15.9%)	56 (20.7%)	86 (31.9%)
Initial deployment cost (2020$)	$986,618	$999,760	$1,973,236	$1,999,520
Life-cycle wrong-way driving crash risk reduction	27.18 (27.4%)	11.33 (38.0%)	45.24 (45.7%)	18.0 (60.3%)
Life-cycle injury savings benefits (2020$)	$116,282,439	$54,554,317	$193,564,190	$86,510,312
Life-cycle costs (2020$)	$1,893,928	$1,741,150	$3,787,857	$3,482,300
Life-cycle benefit–cost ratio	61.40	31.33	51.10	24.84

Comparison of Existing FTE RFB and LED Sites

For the last step of the methodology, the existing FTE RFBs and LEDs were compared. This comparison illustrates the actual injury savings that are being realized by FTE because of these countermeasures, in addition to the already discussed potential savings because of deployments that are not currently implemented. As of February 2020, RFBs have been implemented at 18 ramps for 33 months and LEDs have been implemented at 17 ramps for 65 months. The previously mentioned turnaround percentages of 70.8% (RFBs) and 21.3% (LEDs) include both daytime and night-time WWD detections. Most FTE WWD crashes and fatalities occur at night (Figure 3), so it is important for any deployed countermeasures to be effective at night. For the RFBs, 27 of 46 night-time WWD detections turned around (turnaround percentage of 58.7%), compared with 12 of the 82 night-time WWD detections for the LEDs (turnaround percentage of 14.6%). This shows that the RFBs are more effective at reducing WWD during night-time hours when it is more common and more often results in severe crashes.

Table 5 shows the life-cycle and implementation period benefits and costs of the existing FTE RFBs and LEDs. Even though the RFBs have been active for almost 3 years less than the LEDs, they have prevented about one more WWD crash and provided almost $5 million more in injury savings. For the life cycle, it is estimated that the RFBs will prevent ten WWD crashes while the LEDs will prevent three. The RFBs have a much higher life-cycle B/C ratio (35.97) compared with the LEDs (20.82), even though they have higher costs. These results show that while both countermeasures provide considerable savings, the RFBs provide more value, especially during night-time when most WWD occurs.

Table 5.

Benefits and Costs of Existing Florida’s Turnpike Enterprise Rectangular Flashing Beacon (RFB) and Light-Emitting Diode (LED) Wrong-Way Driving Countermeasures

Parameter	RFBs	LEDs
Number of ramps	18	17
Months active (through February 2020)	33	65
Initial deployment costs (2017$)	$563,850	$351,379
Implementation period wrong-way driving crash risk (WWCR) reduction	2.75	1.60
Implementation period costs (2017$)	$693,899	$498,631
Implementation period injury savings benefits (2017$)	$12,279,156	$7,517,793
Implementation period benefit–cost (B/C) ratio	17.70	15.08
Life-cycle WWCR reduction	10.00	2.95
Life-cycle costs (2017$)	$1,082,376	$611,951
Life-cycle injury savings benefits (2017$)	$38,936,075	$12,741,341
Life-cycle B/C ratio	35.97	20.82

Summary and Conclusion

Freeway WWD crashes are more likely to be fatal than other freeway crashes. Additionally, more fatalities occur in WWD fatal crashes compared with non-WWD fatal crashes. Advanced ITS WWD countermeasures can effectively prevent many wrong-way drivers from entering the mainline. The success of RFB and LED WWD countermeasures on the FTE toll road network shows the potential of these devices. However, very limited previous research determined the financial benefits of these countermeasures because of WWD crash and associated injury reductions. Additionally, no studies have ever estimated the savings that could be achieved by future deployments of these countermeasures. This paper develops a six-step methodology that agencies can use to estimate the potential savings because of advanced WWD countermeasures and compare between different countermeasure types. The developed methodology is applied to the FTE network to illustrate its procedures, compare the economic performance of RFB and LED countermeasures, and identify the benefits of existing deployments.

Analysis of FTE WWD crashes from 2011 to 2016 showed that 13 of the 53 WWD crashes were fatal, resulting in 16 fatalities. The estimated cost of injuries because of these crashes was about $37 million per year, which was higher than the comprehensive cost of $24 million because of the high WWD fatality rate. Most of the FTE WWD crashes (87%) occurred at night, including 11 of the 13 fatal crashes. The average injury cost per WWD crash on Florida limited access facilities was about $4.7 million.

Next, costs, effectiveness, and lifespan information were collected for RFB and LED countermeasures to allow for comparison between them. Predicted WWCR reductions for roadway segments were used to estimate the reduction in WWD crashes at all 216 FTE exits that currently do not have RFB or LED countermeasures for a 10-year life cycle. Injury savings were then calculated for RFBs and LEDs based on these WWCR reductions. Engineering economic analyses were then used to determine life-cycle B/C ratios for all 216 FTE exits and rank them. The total life-cycle injury savings were $424 million for RFBs and $144 million for LEDs if they were equipped at all exits. Because of the RFBs’ improved savings, they had a higher overall B/C ratio than the LEDs (23.20 compared with 13.13), even though RFBs had higher costs.

Since it is not realistic to deploy these countermeasures at all exits at once, various deployment scenarios were tested. First, only the 103 exits where the percentage of total benefits exceeded the percentage of total costs were considered. Deploying RFBs or LEDs at these exits, which contain 40% of the total ramps, would provide 70% of the total WWCR reduction. RFBs would provide $296 million in injury savings, while the LEDs would provide $100 million. Next, capital investment levels of $1 million and $2 million were considered. For each investment level, LEDs could be deployed at more ramps than RFBs because of their lower costs. However, the better performance of the RFBs overcame this difference in cost, resulting in the RFBs providing substantially more savings. With an initial investment of $1 million, RFBs could be deployed at 28 ramps and provide similar savings as an initial investment of $3.4 million to deploy LEDs at 145 ramps. Investing $2 million to deploy RFBs would provide more savings than equipping all 216 FTE exits with LEDs.

The existing FTE RFB and LED deployments were also compared to further show their benefits. The 18 RFB sites had estimated life-cycle injury savings of $38.9 million compared with $12.7 million for the 17 LED sites. Through February 2020, the RFBs have provided injury savings of about $12.3 million in 33 months, while the LEDs have provided injury savings of $7.5 million in 65 months. The RFBs have also been more effective in causing vehicles to turn around at night (58.7% turnarounds compared with 14.6% turnarounds for the LEDs), which is important, since 87% of the WWD crashes and 85% of fatal WWD crashes on the FTE system occur at night.

This paper develops and demonstrates a methodology that agencies can use to estimate injury savings because of future advanced WWD countermeasure deployments and compare between countermeasures. It also shows the massive injury savings that can be obtained by deploying these countermeasures for the FTE system. No previous research quantified these savings for sites that do not currently have these countermeasures. It is believed that this methodology can be transferred to other networks with no major issues. Future research will test the scalability of this methodology by applying it to all Florida limited access facilities. By showcasing the benefits of both LED and RFB WWD countermeasures and conducting various comparisons between them, the findings from this paper can help roadway agencies decide if one or both of these technologies would be effective on their systems. Even if these countermeasures are only deployed at a few ramps, they could still provide millions of dollars in savings and prevent WWD crashes and fatalities, making highway travel safer and more efficient.

Footnotes

Author Contributions

The authors confirm contribution to the paper as follows: study conception and design: A. Sandt, H. Al-Deek; data collection: A. Sandt, H. Al-Deek; analysis and interpretation of results: A. Sandt, H. Al-Deek; draft manuscript preparation: A. Sandt, H. Al-Deek. All authors reviewed the results and approved the final version of the manuscript.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The research discussed in this paper was funded by the Florida’s Turnpike Enterprise (FTE), award number 5046.

The opinions, findings, and conclusions expressed in this paper are those of the authors and not necessarily those of FTE, the Florida Department of Transportation, or the U.S. Department of Transportation.

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