Research, Development, and Technology

Turner-Fairbank Highway Research Center

6300 Georgetown Pike

McLean, VA 22101-2296

PUBLICATION NO. FHWA-HRT-23-011 DECEMBER 2022 

Signing, in Combination with Lane Markings,

in Advance of Lane-Reduction Transitions
FOREWORD

The objective of the Transportation Pooled Fund Program’s Traffic Control Device (TCD) 

Consortium is to assemble a consortium of regional, State, and local entities, other appropriate 

organizations, and the Federal Highway Administration to establish a systematic procedure to 

select, test, and evaluate existing and new TCDs that will support changes to the Manual on 

Uniform Traffic Control Devices and interim approvals. 

The purpose of this study is to explore driver behavior when exposed to four warning signs: two 

advance warning signs, and two lane line transition markings. This study quantifies driver 

behavior by investigating when drivers recognize that the lane would end, prepare to change 

lanes, and execute a lane change. The goal of this work is to assess driver understanding and 

behavior when faced with new and traditional lane-reduction roadway markings and signing. 

This report is of interest to engineers, planners, and other researchers and practitioners who are 

concerned with road users’ ability to comprehend and follow lane-reduction transitions correctly.

Brian P. Cronin, P.E. 

Director, Office of Safety and Operations 

Research and Development

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation 

(USDOT) in the interest of information exchange. The U.S. Government assumes no liability for 

the use of the information contained in this document. 

The U.S. Government does not endorse products or manufacturers. Trademarks or 

manufacturers’ names appear in this report only because they are considered essential to the 

objective of the document. 

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high-quality information to serve 

Government, industry, and the public in a manner that promotes public understanding. Standards 

and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its 

information. FHWA periodically reviews quality issues and adjusts its programs and processes to 

ensure continuous quality improvement. 

Recommended citation: Federal Highway Administration, Signing, in Combination with Lane 

Markings, in Advance of Lane-Reduction Transitions (Washington, DC: 2022) 

https://doi.org/10.21949/1521954 
TECHNICAL REPORT DOCUMENTATION PAGE

1. Report No.

FHWA-HRT-23-011

2. Government Accession No. 3. Recipient’s Catalog No.

4. Title and Subtitle

Signing, in Combination with Lane Markings, in Advance of 

Lane-Reduction Transitions

5. Report Date

December 2022

6. Performing Organization Code: 

7. Author(s)

Matthew Marchese (ORCID: 0000-0002-6899-8810) and 

Tracy B. Gonzalez (ORCID: 0000-0003-2672-1343) 

8. Performing Organization Report No. 

9. Performing Organization Name and Address

Leidos

6300 Georgetown Pike

McLean, VA 22101

10. Work Unit No.

11. Contract or Grant No.

DTFH61-13-D-00024

12. Sponsoring Agency Name and Address

Traffic Control Devices Pooled Fund Study

13. Type of Report and Period Covered

Final Report; June 2017–February 2019

14. Sponsoring Agency Code

HRSO-30

15. Supplementary Notes

The Contraction Officer’s Representative was Brian Phillips (ORCID: 0000-0002-8426-0867). The Task Order 

Contracting Officer’s Representative was Michelle Arnold (ORCID: 0000-0001-5088-8800). 

16. Abstract

Roadway lane-reduction transitions have long been reported to be problematic for drivers. Whether this problem 

is the result of a lack of understanding of lane-reduction signing or lane markings, a simple failure to comply with 

such markings, or other unidentified factors is unknown. This study, completed in 2019, explored driver behavior 

when exposed to four warning signs, two advance warning signs, and two lane line transition markings. The 

warning signs included traditional and new designs. Some of the new designs have currently been adopted by 

State departments of transportation. This study quantified driver behavior by investigating when drivers 

recognized that the lane would end, prepared to change lanes, and executed a lane change. The inclusion of 

advance warning signs resulted in earlier recognition of lane termination. Dotted-with-solid-white lane line 

transition markings resulted in earlier lane changes. 

17. Key Words

Lane markings, lane-reduction signing, MUTCD, 

pavement markings, driver behavior

18. Distribution Statement

No restrictions. This document is available to the public 

through the National Technical Information Service, 

Springfield, VA 22161.

http://www.ntis.gov

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this page)

Unclassified

21. No. of Pages

30

22. Price

N/A

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized
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iii

TABLE OF CONTENTS

CHAPTER 1. INTRODUCTION ................................................................................................ 1

Objectives................................................................................................................................. 6

CHAPTER 2. METHOD .............................................................................................................. 7

Stimuli ...................................................................................................................................... 7

Participant Groups and Variables ........................................................................................ 7

Lane Transition Markings ................................................................................................... 7

Sign Combinations .............................................................................................................. 9

Lane-Reduction Arrow Markings and Lane Assignment ................................................. 12

Stimuli Responses.................................................................................................................. 12

Right Merge Lane Trials ................................................................................................... 13

Left Through Lane Trials .................................................................................................. 13

Participants ............................................................................................................................ 13

Procedure ............................................................................................................................... 14

Measures ................................................................................................................................ 14

Analysis Approach ................................................................................................................ 15

CHAPTER 3. RESULTS ............................................................................................................ 17

Response Times—Right Lane Ends .................................................................................... 17

Warning Sign .................................................................................................................... 17

Advance Warning Sign ..................................................................................................... 17

Interaction: Lane Line Transition Markings and Advance Warning Sign ........................ 17

Interaction: Warning Sign and Advance Warning Sign ................................................... 17

Nonsignificant Results ...................................................................................................... 18

Response Times—Prepare to Change Lanes...................................................................... 18

Warning Sign .................................................................................................................... 18

Advance Warning Sign ..................................................................................................... 18

Interaction: Lane Line Transition Marking and Advance Warning Sign ......................... 18

Interaction: Warning Sign and Advance Warning Sign ................................................... 18

Nonsignificant Results ...................................................................................................... 19

Response Times—Change Lanes ......................................................................................... 19

Lane Line Transition Markings ........................................................................................ 19

Warning Sign .................................................................................................................... 19

Advance Warning Sign ..................................................................................................... 19

Interaction: Lane Line Transition Markings and Warning Sign ....................................... 19

Interaction: Warning Sign and Advance Warning Sign ................................................... 19

Nonsignificant Results ...................................................................................................... 20

Between Response Times—Right Lane Ends and Prepare to Change Lanes ................. 20

Age Group ......................................................................................................................... 20

Advance Warning Sign ..................................................................................................... 20

Interaction: Gender and Advance Warning Sign .............................................................. 20

Interaction: Warning Sign and Advance Warning Sign ................................................... 20

CHAPTER 4. DISCUSSION ..................................................................................................... 21

APPENDIX .................................................................................................................................. 23

REFERENCES ............................................................................................................................ 25
iv

LIST OF FIGURES

Figure 1. Illustration. Examples of lane-reduction transition markings (FHWA 

2009). ...............................................................................................................................1

Figure 2. Illustration. Symbolic lane-reduction warning sign, W4-2 (FHWA 2009). .....................2

Figure 3. Illustration. Text lane-reduction warning sign, W9-2 (FHWA 2009). .............................2

Figure 4. Illustration. Optional additional advance lane-reduction transition sign, 

W9-1 (FHWA 2009). ......................................................................................................2

Figure 5. Illustration. Lane-reduction transition sign W20-X3 used in Iowa 

(Iowa DOT 2017). ...........................................................................................................3

Figure 6. Illustration. Lane-reduction transition sign W9-2L-DE used in Delaware 

and Maryland (Delaware DOT 2011). ............................................................................4

Figure 7. Illustration. Americanized version of work zone sign from the Vienna 

Convention G12a (Shaw et al. 2017). .............................................................................4

Figure 8. Screenshot. Dotted line lane-reduction transition marking. .............................................8

Figure 9. Screenshot. Dotted-line-plus-solid-white-line lane-reduction transition 

marking. ...........................................................................................................................9

LIST OF TABLES

Table 1. Sign configurations (Delaware DOT 2011; FHWA 2009; Iowa DOT 2017; 

Shaw et al. 2017). ..........................................................................................................10

Table 2. Arrow markings and lane-assignment conditions............................................................12

Table 3. Trials ................................................................................................................................23
v 

LIST OF ACRYNOMS

DOT department of transportation 

FHWA Federal Highway Administration

MUTCD Manual on Uniform Traffic Control Devices for Streets and Highways

TCD Traffic Control Devices

PFS Pooled Fund Study

1 

CHAPTER 1. INTRODUCTION

The Traffic Control Device (TCD) Pooled Fund Study (PFS) addresses human factors and 

operations issues through the systematic evaluation of existing and new TCDs. As a part of this 

effort, the Federal Highway Administration (FHWA) Human Factors Team evaluated signing in 

advance of lane reductions. A lane-reduction transition occurs when the number of through lanes 

is reduced between interchanges or intersections. Where pavement markings are used, the 

Manual on Uniform Traffic Control Devices for Streets and Highways (MUTCD) specifies in 

section 3B.09 that lane-reduction transition markings are used to guide traffic through the 

transition areas (FHWA 2009). Figure 1 shows two examples of lane-reduction transition 

markings from the MUTCD (FHWA 2009). 

Source: FHWA. 

Figure 1. Illustration. Examples of lane-reduction transition markings (FHWA 2009). 
2 

The 2009 edition of the MUTCD recommends the placement of the Lane Ends (W4-2) sign 

(figure 2) or the text version LANE ENDS MERGE LEFT (RIGHT) (W9-2) sign (figure 3) for a 

lane-reduction transition (FHWA 2009). The recommended placement of either sign depends on 

the posted speed or the 85th percentile speed of the roadway. This advance placement distance 

(d) is provided in table 2C-4 of the MUTCD (FHWA 2009). For example, if the posted speed 

limit of a roadway is 40 mph, then it is recommended that the warning sign should be placed 

670 ft before the beginning of the taper. Similarly, for a speed of 60 mph, d = 1,100 ft. 

Source: FHWA. 

Figure 2. Illustration. Symbolic lane-reduction warning sign, W4-2 (FHWA 2009). 

Source: FHWA. 

Figure 3. Illustration. Text lane-reduction warning sign, W9-2 (FHWA 2009). 

The 2009 edition of the MUTCD provides an option to use the RIGHT (LEFT) LANE ENDS 

(W9-1) sign (figure 4) in advance of the W4-2 sign or the W9-2 sign (FHWA 2009). The 

purpose for using this additional sign is to provide more time for drivers to safely make the 

appropriate merging maneuver. It is recommended that the RIGHT W9-1 sign be placed adjacent 

to the lane-reduction arrow pavement marking. For speeds less than 45 mph, lane-reduction 

arrows are optional per MUTCD provisions. 

Source: FHWA. 

Figure 4. Illustration. Optional additional advance lane-reduction transition sign, W9-1 

(FHWA 2009). 
3 

Several studies have suggested that the W4-2 symbol has a relatively low comprehension rate. 

Researchers reported 61 percent comprehension rate among 489 drivers from either Texas, 

Idaho, or Alberta, Canada (Dewar et al. 1997). This study scored written responses to pictures of 

the 1988 MUTCD version of W4-2, which lacked the three dashes shown in figure 2. A “merge 

left” response was scored as partially correct in their protocol, and “road narrows” was scored as 

incorrect. Whether this scoring accurately reflects understanding of the W4-2 can be questioned; 

merging left is a correct response to the realization that a lane is ending, and if a driver merged 

into the adjacent lane after recognizing that the number of lanes will reduce, the same result 

(merging into the adjacent lane) would be appropriate. Thus, it is uncertain how many of the 

drivers that comprehended the sign “incorrectly” in the Dewar et al. (1997) study would have 

stayed in the terminating lane later than drivers who comprehended the sign “correctly.” 

Picha, Hawkins, and Womack (1995) reported on several studies conducted over a 5-yr period 

that examined driver comprehension of various lane-reduction signs. Participants were presented 

with eight lane-reduction signs and six forced-choice responses. Only one response was 

considered correct. Signs selected were a combination of standard W4-2 and W9-1 signs in 

addition to alternative designs similar to the MUTCD guidance provisions. The 1988 and 2000 

MUTCD versions of W4-2 garnered correct selections from about 71 percent of respondents. 

The text versions of the right lane ends, W9-1, received significantly more correct selections 

(81 percent) than the W4-2 based signs, but about 20 percent of respondents still selected 

incorrect choices. 

The MUTCD provides W4-2, W9-1, and W9-2 signs for lane-reduction transitions. W4-2 is used 

in place of W9-1 because it has greater legibility distance and does not require English literacy. 

Several States supplement the MUTCD with other warning signs. A few alternatives used by 

States are shown and discussed in the immediate, following paragraphs. These signs (shown in 

figure 5 through figure 7) do not comply with MUTCD provisions. State departments of 

transportation (DOTs) and local jurisdictions are required to use MUTCD-compliant signs. If a 

State DOT or local jurisdiction is interested in using a new TCD or a different application of an 

existing device, it must receive approval to experiment from FHWA using the MUTCD 

experimentation process (FHWA 2009).

The MERGE (W20-X3) warning sign shown in figure 5 is used mainly in Iowa, Minnesota, and 

Missouri. The LANE ENDS (W9-2L-DE) sign shown in figure 6 is used in Delaware and 

Maryland. The warning sign shown in figure 7 is a noncompliant variation of the W4-2-PI that is 

not currently in State or Federal MUTCD. 

© 2017 Iowa DOT.

Figure 5. Illustration. Lane-reduction transition sign W20-X3 used in Iowa

(Iowa DOT 2017). 
4 

© 2009 Delaware DOT.

Figure 6. Illustration. Lane-reduction transition sign W9-2L-DE used in Delaware and 

Maryland (Delaware DOT 2011). 

© 2017 Shaw.

Figure 7. Illustration. Americanized version of work zone sign from the Vienna 

Convention G12a (Shaw et al. 2017). 

The use of lane-reduction signing practices that deviate from MUTCD guidance is an indication 

of a perceived need for more effective signing. However, inconsistent and nonstandard signing 

and marking across and within States may lead to problems in driver comprehension, especially 

for drivers travelling outside of their local jurisdictions. A few recent studies have evaluated 

noncompliant, alternative lane-reduction transition signs for work zones. One study sponsored by 

the Smart Work Zone Deployment Initiative and FHWA evaluated various signs used in work 

zones in the United States, Canada, United Kingdom, Europe, and other countries 

(Shaw et al. 2017). Following a process that used survey data to select lane transition signs from 

a plethora of alternatives, the authors selected three sign alternatives to evaluate in a driving 

simulation. Those signs were W4-2, as shown in figure 2; W20-X3, as shown in figure 5; and an 

Americanized version of the Vienna Convention G12a sign similar to that shown in figure 7. 

The three sign configurations were presented in a driving simulation. The results of the study 

were inconclusive. Although the authors asserted that the W4-2 sign was less well understood, 

they had some validity concerns regarding the design of the questionnaire conducted after the 

test. It offered four, forced-choice responses for two of the signs and only three responses for the 

other. Also, one of the responses was at least partially correct: “[T]raffic in the [through] lane 

should yield to [drivers in the terminating] lane.” This response was always presented before the 

more correct response: “[T]raffic in the [terminating] lane should merge into the [through] lane.”

The former alternative was not offered as a response to W20-X3. The driving behavior measures 

were merge location, average speed, difference between entry speed, and speed at the time the 

participant changed lanes. Most of the participants changed lanes before reaching the signs that 

were the subject of the experiment. In other words, most of the subjects changed lanes before 

coming into proximity of the advance warning sign, which read, “[RIGHT/LEFT] LANE
5 

CLOSED AHEAD,” or they changed lanes at the beginning of the trial, presumably because they 

preferred the other lane. Of those participants who changed lanes after arriving within sight 

distance of the subject signs, there was no significant difference in speed or merge location. 

After reporting no significant differences in merge location, the authors asserted that the 

nonsignificant difference that showed W4-2 as having a later mean merge location than the other 

two signs indicated that W4-2 was less effective than the other two signs. 

It should be noted that there is no general agreement on whether late or early merges are better. 

When traffic is heavy, late merges resulted in better operations. In regard to safety, the 

differences observed between late and early merge were within the bounds of chance. The only 

significant difference between the three sign configurations was in the amount of speed reduction 

observed among drivers who changed lanes after arriving within sight of the subject signs. The 

W4-2 and W20-X3 signs resulted in a significantly larger speed reduction than for the 

Americanized G12a. The authors interpreted the larger speed reduction as an indication that 

W4-2 presents a greater safety risk than the other two signs. Maximum deceleration, which 

would provide an indication of abrupt braking that poses a safety risk, was not reported. 

A field evaluation of driver reactions to the W20-X3 sign compared with driver reactions to the 

W4-2 sign was conducted at a work zone in Missouri (Edara, Zhu, and Sun 2014). The data came 

from 1.5 h of observation at the same work zone on two different days. On the first day, the 

W20-X3 sign was placed on the terminating-lane side, and the left/right lane closed sign was 

placed on the through-lane side. On the second day of observation, W4-2 signs were placed on 

both sides of the road. The study measured driver speed and open-lane occupancy. The 

“MERGE” text and arrow symbol configuration of W20-X3 sign resulted in 6 percent more 

vehicles (11 percent more light vehicles) being in the through lane upstream of the merge signs. 

Mean speeds remained consistent between sign configurations or speed measurement locations 

(at test-sign configuration location and at the beginning of the taper). The authors concluded that 

the W20-X3 configuration was an acceptable alternative to W4-2 sign recommendations. They 

also concluded that the W20-X3 configuration resulted in earlier merges by passenger vehicle 

drivers (but not trucks), which might suggest a safety advantage. The authors did not indicate 

which lane was closed on the different days, which were 2 days apart. If different lanes were 

closed on each day (which would seem likely), then this difference in lane closures could have 

influenced differences in lane occupancy.

The previous literature on lane-reduction signing suggests valuable insights for the evaluation of 

alternatives to W4-2 at lane-reduction transitions.

1. The behavioral objective for each sign configuration needs to be made explicit before 

testing begins. 

2. If a sign or configuration of signs is intended to replace configurations that implement 

W4-2, as recommended in the MUTCD, because the W4-2 is thought to be poorly 

comprehended, then the evaluation should assess comprehension of the entire 

configuration (i.e., advance signs, W4-2 or alternatives, and lane-reduction arrows).

3. Comprehension tests should reflect what participants would do in response to a sign 

rather than whether they can express the sign’s meaning in a way acceptable to the 
6 

examiner. If the participant would merge into the through lane before the taper in 

response to the sign, then it should not matter whether the participant said the sign 

meant merge left or road narrows.

In a previous study conducted for the TCD PFS (Balk and Jackson 2016), researchers

recommended using dotted lines to mark the lane reduction. In addition, the authors 

recommended further testing of the inclusion of a solid white line to the left of the dotted line 

transition markings, because there was some evidence that the solid line discouraged drivers in 

the through lane from moving into the terminating lane. Although the solid white line resulted in 

slightly better comprehension of the transition markings, there was some concern that it might 

discourage drivers from early merges. Because lane lines and signs are intended to work 

synergistically, they should be tested together. The researchers tested the dotted line markings 

without signs or arrow pavement markings to ensure that participants were responding to the 

dotted lines and not other environmental cues (i.e., arrows or signs). The current study attempted 

to isolate comprehension of the signs in a similar manner, and researchers also tested the signs in 

complete context, with arrow markings and the dotted line markings recommended in the 

previous PFS. 

OBJECTIVES

The current research expands on Balk and Jackson’s 2016 study by evaluating existing lane line 

marking patterns in combination with standard signs as well as potential new designs for 

lane-reduction transitions. The goal of this project was to determine the effects of specific signs, 

in combination with markings, in terms of:

• Merging behavior (i.e., early merging) before lane-reduction transitions.

• Understanding and time of comprehension of the intended message conveyed at 

lane-reduction transitions (from both the terminating lane and the left-adjacent lane). 
7 

CHAPTER 2. METHOD

STIMULI

Drafting and three-dimensional modeling software were used to generate virtual four-lane, 

undivided highways with reasonably realistic surrounding environments using real roadway 

geographic information system (known as “GIS”) data. On completion of the roadway and 

environment, “fly-through” videos, which create the illusion of moving through the environment, 

were created. To reduce the possibility of a participant’s response being influenced by repeated 

exposure to identical surrounding environments, four surrounding environments were used: a 

dense urban environment, a moderate urban environment, a rural environment, and a wooded 

environment. Driving environments were strictly superficial and had no impact on traffic flow. 

Simulated traffic was used in the oncoming lane to mimic a more realistic driving environment. 

Traffic was absent from the participant’s direction of travel to simulate free-flow conditions. 

These conditions ensured that the participant’s response was influenced only by the roadway’s 

lane markings and signing. 

PARTICIPANT GROUPS AND VARIABLES 

Each participant was assigned to one of two lane-reduction transition marking groups. Within 

each group, there were four variables: lane transition markings—two conditions; warning 

signs—eight conditions; advance warning signs—three conditions; and lane assignment—two

conditions. The result was a total of 56 trials for each participant in each group. See the appendix 

for a complete list of trial combinations. 

Lane Transition Markings 

The lane markings selected for the participant groups were dotted line (figure 8) and dotted lines 

with solid line to the left of the dotted line (figure 9). Balk and Jackson (2016) recommended 

these two selected lane line groups. The taper and lane transition marking length were based on a 

posted speed limit of 45 mph (See MUTCD table 2C-4) (FHWA 2009). 
8 

Source: FHWA.

Figure 8. Screenshot. Dotted line lane-reduction transition marking.
9 

Source: FHWA

Figure 9. Screenshot. Dotted-line-plus-solid-white-line lane-reduction transition marking. 

Sign Combinations

Four lane-reduction warning signs and two advance warning signs were used. Of the six warning 

and advance warning signs used, three were from the FHWA MUTCD (W4-2, W9-2, and W9-1) 

(FHWA 2009). The remaining are not compliant with MUTCD provisions, such that if a State 

DOT or local jurisdiction is interested in using these signs, it must first receive approval to 

experiment from FHWA. Of the three noncompliant signs, two were from State MUTCDs 

(W20-X3 and W9-2L-DE), and one was a proposed custom design not currently found on 

roadways (W4-2-PI). 

Warning sign and advance warning sign placement were based on a posted speed limit of 45 mph 

(See MUTCD table 2C-4) (FHWA 2009). 

To ensure active participant engagement, four non-lane-reduction signs were used twice, once 

for each lane assignment (See table 1, conditions 13–16). These trials had no lane reduction and 

were not used in the analysis. Participants who incorrectly responded to at least 50 percent of the 

non-lane-reduction trials were excluded from analysis and replaced by another participant of the 
10 

same age group and gender. See the Stimuli Response section following in this chapter for an 

explanation of what is considered a correct response for the non-lane-reduction trials. All 16 sign 

configurations were within-subject tested (i.e., all participants saw all sign configurations). The 

16 sign configurations can be seen in table 1. Note that signs W20-X3, W9-2L-DE, and W4-2-PI

do not comply with MUTCD provisions. 

Table 1. Sign configurations (Delaware DOT 2011; FHWA 2009; Iowa DOT 2017; Shaw et 

al. 2017). 

Sign 

Configuration 

Condition 

Lane 

Reduction

Advance 

Warning 

Sign 

Advance 

Warning Sign 

Image 

Warning 

Sign 

Warning Sign 

Image 

1 Yes None None W4-2 

2 Yes None None W9-2 

3 Yes None None W20-X3

© 2017 Iowa DOT.

4 Yes None None W9-2L-DE

© 2009 Delaware DOT.

5 Yes W9-1 W4-2 

6 Yes W9-1 W9-2 
11 

Sign 

Configuration 

Condition 

Lane 

Reduction

Advance 

Warning 

Sign 

Advance 

Warning Sign 

Image 

Warning 

Sign 

Warning Sign 

Image 

7 Yes W9-1 W20-X3

8 Yes W9-1 W9-2L-DE

9 Yes W4-2-PI

© 2017 Shaw.

W4-2 

10 Yes W4-2-PI W9-2 

11 Yes W4-2-PI W20-X3

12 Yes W4-2-PI W9-2L-DE

13 No None None W23-2 
12 

Sign 

Configuration 

Condition 

Lane 

Reduction

Advance 

Warning 

Sign 

Advance 

Warning Sign 

Image 

Warning 

Sign 

Warning Sign 

Image 

14 No None None W19-1 

15 No None None W1-10b 

16 No None None W1-10c 

Note: Unless indicated otherwise, all illustrations source: FHWA (2009). 

Lane-Reduction Arrow Markings and Lane Assignment 

Sign configuration conditions 1–12 had trials with and without lane-reduction arrow markings. 

Sign configuration conditions 13 and 14 did not have lane-reduction arrow markings for all four 

sign configurations because of the absence of lane reduction. All sign configurations and 

lane-reduction arrow marking combinations had trials with lane assignments in the right merge 

lane and left through lane. Trials in the right merge lane experienced a lane reduction, but trials 

in the left through lane did not. Trials were blocked in groups of 14 (14 right merge, 14 left 

through, 14 right merge, 14 left through) and then were randomized within each block (table 2). 

Table 2. Arrow markings and lane-assignment conditions. 

Condition Lane Assignment Lane Arrows Used

1 Right merge lane Yes 

2 Right merge lane No

3 Left through lane Yes 

4 Left through lane No

STIMULI RESPONSES

Participants were instructed to imagine they were driving in the lane pictured in the provided 

stimuli. Using high-precision stimulus presentation and response-recording software, participants 

were asked to respond appropriately and in sequential order using three predefined responses. If 

responses were selected out of sequential order, those trials were excluded from analysis. 
13 

Right Merge Lane Trials

In right merge lane-assignment trials, the participant’s viewpoint was from a lane that may 

eventually end. Participants were asked to respond, when appropriate and in sequential order, 

using the three labeled buttons in front of them: 

1. Right lane ends. 

2. Prepare to change lanes. 

3. Change lanes. 

The research team instructed participants to press the “Right lane ends” button when the 

participants determined the lane they were traveling in (the right lane) would eventually 

terminate. The team instructed participants to press the “Prepare to change lanes” button when 

the participants would begin lane-change preparations, such as when checking mirrors and 

engaging turn signals. Finally, the team instructed participants to press the “Change lanes” 

button when the participants would normally execute the lane change. Participants were also 

instructed to respond only if necessary, and responses may not be necessary on some trials. Any 

response for nonlane-reduction trials was considered incorrect.

Left Through Lane Trials

In left through lane-assignment trials, the participant’s viewpoint was adjacent to a right lane that 

may eventually end. Participants were asked to imagine there was a vehicle in the right lane 

about 10 ft ahead. Unlike during the right merge lane trials, participants were instructed to 

anticipate the other vehicles’ maneuvers and not their own. The responses were the same as for 

the right merge lane scenarios: 

1. Right lane ends. 

2. Prepare to change lanes. 

3. Change lanes. 

The research team instructed participants to press the “Right lane ends” button when the 

participants determined the adjacent lane would eventually terminate. The team instructed 

participants to press the “Prepare to change lanes” button when the participants estimated that the 

vehicle in the adjacent lane would begin lane change preparations (e.g., check their mirrors, 

engage turn signals). The team instructed participants to press the “Change lanes” button when 

the participants estimated that the other vehicles would begin the lane change. The participants 

were instructed to only respond if they determined that the right lane would end, and they were 

told that responses may be unnecessary for some trials. Responses for non-lane-reduction trials 

were considered incorrect.

PARTICIPANTS

In total, 112 licensed drivers participated: two groups of 56 participants with equal numbers of 

males and females older and younger than 45 yr. Each was paid $40 for his or her participation.
14 

PROCEDURE

On arrival, participants were greeted and asked to review and sign a record of informed consent. 

Participants’ visual acuity was checked to ensure a minimum 20/40 vision in at least one eye 

(i.e., the minimum to obtain a driver’s license in most States). Next, participants were seated 

approximately 8 ft from a 60-inch LCD monitor used for video presentations. A table in front of 

the participant supported a three-button response pad. Instructions read as follows: 

The purpose of this study is to identify the best way to indicate to drivers when they need 

to change lanes because of roadway conditions ahead. We are going to show you a series 

of videos of a four-lane highway. Each video shows a driver’s view of the roadway as it 

would appear when traveling at 45 mi/h. Sometimes the view will be from the left lane, 

sometimes from the right. 

In videos from the right lane your task is to imagine you are driving in a lane that may 

end and you need to decide if you need to change lanes. You should NOT decide to 

change lanes unless it is necessary. If you detect that a lane change will be required 

ahead, press the left button, which is labeled “Right lane ends.” At the location where you 

would start to check your mirrors or engage your turn signals, press the button labeled 

“Prepare to change lanes.” When you are at the point where you would make the lane 

change, press the button labeled “Make lane change.” If you determine that there is no 

lane change, do not respond. When all three buttons are pressed or the video ends with no 

recorded input, the trial will end and continue to the next one. 

Videos in the left lane are like the right lane videos in that you have the same three 

responses. However, the left lane will NEVER end. Instead of imagining that you need to 

make the lane change, you will be trying to anticipate how a vehicle in the right lane may 

behave. For example, imagine there is a vehicle in the right lane about 10 feet in front of 

you. Your task is to first (1) determine that the right lane ends, then (2) estimate when the 

vehicle would prepare to change lanes, and finally (3) estimate when the vehicle would 

begin a lane change. If the right lane does not end, do not enter any responses. 

Prior to starting the experiment, you will be given 6 practice videos, 3 from the right lane 

and 3 from the left lane. Do you have any questions? 

After each participant completed the six practice trials and was comfortable with the task, the 

56 experimental trials began. Total participation time ranged from 25 to 50 min, depending on 

participant response speed and breaks between trials. 

MEASURES

The two dependent measures were the time stamps indicating when the participants selected each 

of the three buttons and the response times between button presses. The time stamps indicating

when the participant pressed the buttons served as the primary measure and provided an 

indication of sign recognition and early versus late merge tendencies as a function of the TCD. 

The response time between the first and second button press served as a secondary measure that 

provides an indication of early- versus late-merge tendencies as a function of the TCD.
15 

ANALYSIS APPROACH

A generalized estimating equation model was used to test the associations between the 

independent variables and the dependent variables (i.e., three response time stamps). When the 

reaction times were analyzed, the normal distribution was specified. The repeated statement was 

specified to account for variability associated with each participant because there were multiple 

responses per participant. 

All independent variables and their pairwise interactions were included in the initial model for 

each analysis. The most nonsignificant effects were removed, and the model was rerun. This 

procedure was repeated until the effects remaining in the model were all significant. 

Nonsignificant main effects were kept in the model if there was a significant interaction with that 

effect. The following independent variables were used in the initial model: gender, age group, 

lane line transition markings, lane assignment, lane-reduction arrows, warning sign, and advance 

warning sign. 

17 

CHAPTER 3. RESULTS

Incorrect responses (i.e., responding out of sequential order, not responding when appropriate) 

were removed from analysis, resulting in 44 to 48 trials per participant. The analysis was 

completed by using the Wald Chi-Squared test.

RESPONSE TIMES—RIGHT LANE ENDS

The “right lane ends” response was the first in the sequence of responses. Its intent was to signify 

the point at which participants recognized the right lane was ending. 

Warning Sign 

Overall, type of warning sign significantly affected “right lane ends” response times, 

χ2(3) = 59.1, p < 0.001. Trials during which warning sign W4-2 (mean [M] = 18.7 s) was present

and trials during which W20-X3 were present (M = 18.9 s) had mean response times that were 

significantly faster than trials with W9-2 (M = 19.5 s) or W9-2L-DE (M = 19.5 s). 

Advance Warning Sign 

Overall, the presence and type of advance warning sign significantly affected “right lane ends” 

response times, χ2(2) = 172.1, p < 0.001. Trials with W4-2-PI (M = 17.4 s) had a mean response 

time that was significantly faster than the mean response time of trials with W9-1 (M = 19.5 s), 

and trials with advance warning sign W9-1 had a mean response time that was significantly 

faster than the mean response times of trials having no advance warning signs present 

(M = 20.6 s).

Interaction: Lane Line Transition Markings and Advance Warning Sign

The interaction between lane transition markings and advance warning signs significantly 

affected “right lane ends” response times, χ2

(2) = 8.3, p = 0.016. When there was no advance 

warning sign present, dotted-with-solid-line transition markings had response times that were 

1.4 s faster than the mean response times of trials with only dotted lane line transition markings. 

No difference in response time was found between lane line transition markings when either of 

the advance warning signs was present.

Interaction: Warning Sign and Advance Warning Sign 

The interaction between warning sign and type of advance warning sign significantly affected 

“right lane ends” response times, χ2

(6) = 89.5, p < 0.001. The warning signs’ effects on “right 

lane ends” response times were significant only when there were no advance warning signs 

present. When no warning signs were present, trials with W4-2 (M = 19.9 s) and trials with 

W20-X3 (M = 20.1 s) had mean response times that were significantly faster than trials with 

W9-2 (M = 21.5 s) or W9-2L-DE (M = 21.4 s). However, when either of the advanced warning 

signs was present, there were no significant differences in mean response time to any of the four 

warning signs. 
18 

Nonsignificant Results 

Gender, age group, lane assignment, and lane-reduction arrows were found to have had no 

significant effect on “right lane ends” response times. 

RESPONSE TIMES—PREPARE TO CHANGE LANES

The “prepare to change lanes” response was the second in the sequence of responses. Its intent 

was to signify the point at which the participant or the other vehicle (lane assignment: left 

through lane trials) would prepare to change lanes by checking their mirrors or engaging the turn 

signal. 

Warning Sign

Overall, the warning signs had a significant effect on “prepare to change lanes” response times, 

χ2

(3) = 61.9, p < 0.001. Trials during which warning sign W4-2 (M = 22.5 s) was present and 

trials during which W20-X3 (M = 22.6 s) were present had mean response times that were 

significantly faster than trials with W9-2 (M = 22.9 s) or W9-2L-DE (M = 23.0 s). 

Advance Warning Sign 

Overall, advance warning sign had a significant effect on “prepare to change lanes” response 

times, χ2(2) = 120.7, p < 0.001. Trials on which either W4-2-PI (M = 21.9 s) or W9-1 

(M = 22.9 s) was present had mean response times that were significantly faster than trials when 

no advance warning signs present (M = 23.6 s). 

Interaction: Lane Line Transition Marking and Advance Warning Sign 

The interaction between lane transition markings and type of advance warning sign significantly 

affected “right lane ends” response times, χ2(2) = 8.1, p = 0.018. The results for this interaction 

were the same as the effect of “right lane ends” on response times. Only when there was no 

advance warning sign present did the dotted-with-solid lane line transition marking have a faster

average response time on “prepare to change lanes” (M = 22.9 s) than dotted-only lane line 

transition markings (M = 24.2 s). 

Interaction: Warning Sign and Advance Warning Sign 

Overall, the interaction between warning sign and advance warning sign had a significant effect 

on “prepare to change lanes” response times, χ2(6) = 40.3, p < 0.001. When no warning signs 

were present, trials with W4-2 (M = 23.0 s) and trials with W20-X3 (M = 23.2 s) had mean 

response times that were significantly faster than trials with W9-2 (M = 24.1 s) or W9-2L-DE 

(M = 24 s). When the advanced warning sign W9-1 was present, trials with W4-2 (M = 22.7 s) 

and trials with W20-X3 (M = 22.6 s) had mean response times that were significantly faster than 

trials with W9-2L-DE (M = 22.9 s). When advanced warning sign W9-1 was present, there was 

no difference in mean response time for the four warning signs. 
19 

Nonsignificant Results

Age group, lane assignment, and lane-reduction arrows were found to have had no significant 

effect on “prepare to change lanes” response times. 

RESPONSE TIMES—CHANGE LANES

The “change lanes” response was the third in the sequence of responses. Its intent was to signify 

the point at which the participant or the other vehicle (lane assignment left through lane trials) 

would execute the lane change.

Lane Line Transition Markings

Lane line transition markings had a significant effect on “change lanes” response times, 

χ2(1) = 4.2, p = 0.043. Trials that had dotted-with-solid lane line markings had “change lanes” 

response times that were on average significantly faster (M = 25.3 s) than those trials with 

dotted-line-only lane line markings (M = 26.7 s). 

Warning Sign 

Overall, the presence of a warning sign had a significant effect on “change lanes” response 

times, χ2(3) = 28.5, p < 0.001. Trials during which warning sign W4-2 (M = 25.8 s) was present 

and trials during which W20-X3 (M = 225.9 s) were present had mean response times that were 

significantly faster than trials with W9-2 (M = 26.1 s) or W9-2L-DE (M = 26.2 s).

Advance Warning Sign

Overall, the presence of an advance warning sign had a significant effect on the “change lanes” 

response times, χ2(2) = 58.4, p < 0.001. The response times were fastest on average when trials 

had W4-2-PI present (M = 25.5 s). Trials with W4-2-PI had response times that were on average 

significantly faster than those response times of trials with W9-1 present (M = 26.0 s) and when 

there was no advance warning sign present (M = 26.5 s). 

Interaction: Lane Line Transition Markings and Warning Sign 

The interaction between lane line transition markings and type of warning sign significantly 

affected “change lanes” response times, χ2

(3) = 8.16, p = 0.043. Trials that had dotted-with-solid 

lane line transition markings had response times that were on average significantly faster than 

trials with dotted-line-only lane line transition markings when warning signs W9-2L-DE 

(M = 1.3 s), W4-2 (M = 1.5 s), or W9-2 (M = 1.4 s) were present. Lane line transition markings 

did not make a significant difference when the W20-X3 warning sign was present. Trials with 

W9-2 had on average significantly slower response times than trials with W4-2 signs, regardless 

of lane line transition markings. 

Interaction: Warning Sign and Advance Warning Sign 

The interaction between type of warning sign and advance warning sign significantly affected 

“change lanes” response times, χ2

(6) = 21.3, p = 0.002. When no warning signs were present, 
20 

trials with W4-2 (M = 26.2 s) and trials with W20-X3 (M = 26.3 s) had significantly faster mean 

response times than trials with W9-2L-DE (M = 26.8 s). Warning signs did not make a 

significant difference for trials with an advance warning sign present. 

Nonsignificant Results 

Age group, lane assignment, and lane-reduction arrows were found to have had no significant 

effect on “change lanes” response times. 

BETWEEN RESPONSE TIMES—RIGHT LANE ENDS AND PREPARE TO CHANGE 

LANES

Age Group

The average time between responses for older participants was significantly less than the time for 

younger participants, χ2

(1) = 6.1, p = 0.013. On average, the older group (M = 2.9 s) took less 

time to prepare to change lanes after noticing the lane ends than the younger group (M = 4.1 s). 

Advance Warning Sign

Overall, the presence of an advance warning sign had a significant effect on the time between 

responses, χ2

(2) = 68.0, p < 0.001. Trials with no advance warning sign present had the least 

amount of time between recognizing the lane ends and preparing to change lanes (M = 2.9 s). 

Trials with the W9-1 advance warning sign had a mean response time (M = 3.2 s) that was 

significantly longer than the mean response time of trials with the W4-2-PI advance warning sign 

(M = 2.5 s). 

Interaction: Gender and Advance Warning Sign

The interaction between gender and advance warning signs significantly affected time between 

“right lane ends” and “prepare to change” lanes responses, χ2

(2) = 10.6, p = 0.005. The time 

between “right lane ends” and “prepare to change lanes” responses for females was significantly 

shorter than the time between responses for males only when W9-1 (M = 2.9 s, M = 3.6 s) or 

W4-2-PI (M = 3.6 s, 5.4 s) advance warning signs were present. The difference in time between 

responses between males and females was not significant when there was no advance warning 

sign present. 

Interaction: Warning Sign and Advance Warning Sign 

Overall, the interaction between warning sign and advance warning sign had a significant effect 

on time between responses, χ2

(6) = 54.2, p < 0.001. When no advanced warning signs were

present, trials with W9-2 (M = 2.5 s) and trials with W9-2L-DE (M = 2.7 s) had a smaller time 

between responses than trials with W4-2 (M = 3.6 s) and W20-X3 (M = 3.1 s). When either 

advance warning sign W9-1 or W4-2-PI was present, there was no significant difference in 

average time between responses between any of the tested warning signs.
21 

CHAPTER 4. DISCUSSION

The goal of this work was to assess driver understanding and behavior when faced with new and 

traditional lane-reduction roadway markings and signing. Participants responded to various 

stimuli using button-press responses, and the timing of those responses was analyzed to 

determine the effects that lane-reduction signing in combination with lane line transition 

markings are expected to have on: 

• Merging behavior (i.e., moving into the adjacent lane) at lane-reduction transitions. 

• Understanding and time of comprehension of the intended message conveyed at 

lane-reduction transitions (from both the terminating lane and the left-adjacent lane). 

When participants were presented with stimuli that contained advance warning signs, early 

merge behaviors were apparent across all measures, regardless of signing or lane markings. In 

some instances, recognition of lane termination was 3.2 s faster when an advance warning sign 

was present. At 45 mph, this speed provided the driver with an additional 211.2 ft to change 

lanes—just from the addition of an advance warning sign. The results also suggested that the 

effect of different warning signs on driver behavior is not significant when an advance warning 

sign is present. 

Certain signs consistently encouraged early merge behavior, but others did not. When no 

advance warning sign was present, W4-2 frequently encouraged early merging across all three 

responses. In contrast, W9-2 had consistently slower response times across all measures when no 

advance warning sign was present. These results suggest different responses between symbol 

(W4-2) and text-based (W9-2) signing. Both the W9-2L-DE and W20-X3 warning signs, which 

include both symbols and text, had response times that fell between those response times found 

for W4-2 and W9-2. This claim is further supported by the advance warning sign results. 

W4-2-PI, a symbol-based and W4-2 derivative sign, had an average response time for “right lane 

ends” responses that was 2.1 s faster than the average response time for W9-1, a text-based 

advance warning sign. However, further research is required to fully substantiate these claims as 

it is difficult to isolate the ideal warning sign because of a myriad of other external factors that 

were not accounted for, such as familiarity with the signs or participants’ native languages. 

The intent of this study was to expand on the findings from the Balk and Jackson (2016) 

lane-reduction line markings study. From that study, two lane line marking suggestions were 

made, which were included as variables in the current study. Balk and Jackson (2016) found that 

the inclusion of a solid white line in combination with a dotted white line resulted in slightly 

better comprehension of a lane reduction, but there were concerns that the solid white line would 

discourage drivers from making early merges. The results of the current study suggest that this 

concern may be dismissed. Specifically, the significant interaction effects of lane line transitions 

markings and the warning sign on the “change lanes” responses reduced the concern that the 

solid white line would discourage drivers from making early merges. When warning signs W4-2, 

W9-2L-DE, or W9-2 were present, the average response time for “change lanes” was 

significantly faster when a dotted-with-solid line was present as opposed to the presence of a 

dotted-only lane line. It is possible that the inclusion of a solid line in combination with a 

warning sign created a sense of urgency, resulting in an earlier lane change. 
22 

Although lane-reduction arrow markings were a manipulated variable in this study, those 

markings had no significant effects on response times or times between responses. It is possible 

that these insignificant findings could be because of the experimental task and provided stimuli: 

The lane-reduction arrow markings were the final cue before the lane reduction. At that point, 

the participant had already been exposed to three to four other cues. However, this finding 

should not be interpreted as evidence for not using lane-reduction arrows in practice. In this 

study, participants were tasked with identifying lane reductions in an environment with little 

distraction. Lane-reduction arrow markings could still be a necessity in high-traffic-density or 

short-transition scenarios. 

Taken together, these results lead to several conclusions: 

• The addition of an advance warning sign resulted in earlier recognition of lane 

termination.

• There is some evidence that symbol-based warning signs encourage earlier recognition 

and execution of lane changes. 

• In this study, driver behavior was evaluated in a low-traffic-density environment, making 

early lane changes the preferred behavior. However, in higher-traffic-density scenarios, 

early lane changes may not be preferred. 

• The results of this study and Balk and Jackson (2016) suggest that the inclusion of a solid 

white line with a dotted lane line yields better lane-reduction recognition and encourages 

earlier lane changes.
23 

APPENDIX

Table 3 includes the complete list of trial combinations used in the experiment. 

Table 3. Trials 

Trial

Sign 

Configuration 

Condition

Arrow 

Marking 

and Stimuli 

Condition

Advance 

Warning 

Sign

Warning 

Sign Lane Assignment

LaneReduction 

Arrows 

Used

1 1 1 None W4-2 Right merge lane Yes

2 1 2 None W4-2 Right merge lane No

3 1 3 None W4-2 Left through lane Yes

4 1 4 None W4-2 Left through lane No

5 2 1 None W9-2 Right merge lane Yes

6 2 2 None W9-2 Right merge lane No

7 2 3 None W9-2 Left through lane Yes

8 2 4 None W9-2 Left through lane No

9 3 1 None W20-X3 Right merge lane Yes

10 3 2 None W20-X3 Right merge lane No

11 3 3 None W20-X3 Left through lane Yes

12 3 4 None W20-X3 Left through lane No

13 4 1 None Delaware 

W9-2L-DE Right merge lane Yes

14 4 2 None Delaware 

W9-2L-DE Right merge lane No

15 4 3 None Delaware 

W9-2L-DE Left through lane Yes

16 4 4 None Delaware 

W9-2L-DE Left through lane No

17 5 1 W9-1 W4-2 Right merge lane Yes

18 5 2 W9-1 W4-2 Right merge lane No

19 5 3 W9-1 W4-2 Left through lane Yes

20 5 4 W9-1 W4-2 Left through lane No

21 6 1 W9-1 W9-2 Right merge lane Yes

22 6 2 W9-1 W9-2 Right merge lane No

23 6 3 W9-1 W9-2 Left through lane Yes

24 6 4 W9-1 W9-2 Left through lane No

25 7 1 W9-1 W20-X3 Right merge lane Yes

26 7 2 W9-1 W20-X3 Right merge lane No

27 7 3 W9-1 W20-X3 Left through lane Yes

28 7 4 W9-1 W20-X3 Left through lane No

29 8 1 W9-1 Delaware 

W9-2L-DE Right merge lane Yes
24 

Trial

Sign 

Configuration 

Condition

Arrow 

Marking 

and Stimuli 

Condition

Advance 

Warning 

Sign

Warning 

Sign Lane Assignment

LaneReduction 

Arrows 

Used

30 8 2 W9-1 Delaware 

W9-2L-DE Right merge lane No

31 8 3 W9-1 Delaware 

W9-2L-DE Left through lane Yes

32 8 4 W9-1 Delaware 

W9-2L-DE Left through lane No

33 9 1 W4-2-PI W4-2 Right merge lane Yes

34 9 2 W4-2-PI W4-2 Right merge lane No

35 9 3 W4-2-PI W4-2 Left through lane Yes

36 9 4 W4-2-PI W4-2 Left through lane No

37 10 1 W4-2-PI W9-2 Right merge lane Yes

38 10 2 W4-2-PI W9-2 Right merge lane No

39 10 3 W4-2-PI W9-2 Left through lane Yes

40 10 4 W4-2-PI W9-2 Left through lane No

41 11 1 W4-2-PI W20-X3 Right merge lane Yes

42 11 2 W4-2-PI W20-X3 Right merge lane No

43 11 3 W4-2-PI W20-X3 Left through lane Yes

44 11 4 W4-2-PI W20-X3 Left through lane No

45 12 1 W4-2-PI Delaware 

W9-2L-DE Right merge lane Yes

46 12 2 W4-2-PI Delaware 

W9-2L-DE Right merge lane No

47 12 3 W4-2-PI Delaware 

W9-2L-DE Left through lane Yes

48 12 4 W4-2-PI Delaware 

W9-2L-DE Left through lane No

49 13 1 N/A W23-2 Right merge lane N/A

50 13 3 N/A W23-2 Left through lane N/A

51 14 1 N/A W19-1 Right merge lane N/A

52 14 3 N/A W19-1 Left through lane N/A

53 15 1 N/A W1-10b Right merge lane N/A

54 15 3 N/A W1-10b Left through lane N/A

55 16 1 N/A W1-10c Right merge lane N/A

56 16 3 N/A W1-10c Left through lane N/A

N/A = not applicable.
25 

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HRSO-30/12-22(WEB)E Recycled

Recyclable

Recommended citation: Federal Highway Administration, Signing, in Combination 

with Lane Markings, in Advance of Lane‐Reduction Transitions (Washington, DC: 2022) 

https://doi.org/10.21949/1521954