Active Traffic Management: Comprehension, Legibility, Distance, and Motorist Behavior in Response to Selected Variable Speed Limit and Lane Control Signing

508 Captions

Figure 2. Screen capture. VSL scenario of five screens (presented from bottom to top). This screen capture shows a composite of four-lane active traffic management signs with a changeable message sign (CMS) on the gantry to the right. The composite presents the following five sets of signs (bottom to top):

• The first image shows a high occupancy vehicle restriction sign, shown by a diamond shape and the text "2+ ONLY," in the left lane. The other three signs are blank. The CMS shows "REDUCED SPEED ZONE AHEAD."
• The second image shows a speed reduction sign "60 MPH" in the left lane and "45 MPH" in the three right lanes. The CMS shows "REDUCED SPEED ZONE."
• The third image shows a speed reduction sign "45 MPH" in the left lane and "35 MPH" in the three right lanes. The CMS shows "REDUCED SPEED ZONE."
• The fourth image shows a speed limit sign "60 MPH" in all four lanes. The CMS is blank.
• The fifth image shows a high occupancy vehicle restriction sign, which is a diamond with the text "2+ ONLY" in the left lane. The other three signs and the CMSs are blank.

Back

Figure 52. Illustration. Design of scenario 2-stalled vehicle scenario design closing 1 lane (right-center lane-lane 3). This figure depicts six banks of four active traffic management (ATM) signs with a changeable message sign (CMS) on the gantry to the right over a four-lane road. The figure shows an example of ATM sign operation with a stalled vehicle in the second lane from the right between the fourth and fifth banks of ATM signs. The specific layout bottom to top (i.e., the direction of travel) is as follows:

• The first bank of signs shows normal operations-a high occupancy vehicle (two passengers) restriction sign (HOV 2) in the left lane and normal flow of traffic in the other three lanes. The CMS shows "STALLED VEHICLE AHEAD."
• From left to right, the second bank of signs shows HOV 2, normal flow of traffic, lane closure 1 mi ahead, and normal flow of traffic. The CMS shows "STALLED VEHICLE AHEAD."
• From left to right, the third bank of signs shows HOV 2, normal flow of traffic, split-merge, and normal flow of traffic. The CMS shows "STALLED VEHICLE AHEAD."
• From left to right, the fourth bank of signs shows HOV 2, normal flow of traffic, lane closed, and normal flow of traffic. The CMS shows "CENTER LANE CLOSED".
• The fifth bank of signs shows HOV 2 in the left lane and a speed limit of 65 mi/h for the other three lanes. The CMS is blank.
• The sixth bank of signs shows normal operations-HOV 2 in the left lane and normal flow of traffic in the other three lanes. The CMS is blank.

Back

Figure 53. Illustration. Design of scenario 3-vehicle crash scenario design closing two left lanes (lanes 1 and 2). This figure depicts six banks of four active traffic management (ATM) signs with a changeable message sign (CMS) on the right gantry over a four-lane road. The figure shows an example of ATM sign operation with a crashed vehicle and an emergency vehicle in the two left lanes between the fourth and fifth banks of ATM signs. The specific layout bottom to top (i.e., the direction of travel) is as follows:

• The first bank of signs shows a lane closure 1 mi ahead in the left lane and normal operations in the other three lanes. The CMS shows "ACCIDENT AHEAD MERGE RIGHT."
• From left to right, the second bank of signs shows merge right, lane closure 1 mi ahead, and normal operations in the two right lanes. The CMS shows "ACCIDENT AHEAD MERGE RIGHT."
• From left to right, the third bank of signs shows lane closed, merge right, and normal operations in the two right lanes. The CMS shows "ACCIDENT AHEAD MERGE RIGHT."
• The fourth bank of signs shows the two right lanes closed and normal operations in the two right lanes. The CMS shows "RIGHT LANES CLOSED."
• The fifth bank of signs shows a speed limit of 65 mi/h in all lanes. The CMS is blank.
• The sixth bank of signs shows a high-occupancy vehicle (HOV) (two passengers) restriction sign in the left lane (HOV 2) and blank signs above the other three lanes. The CMS is blank.

Back

Figure 54. Illustration. Design of scenario 4-vehicle crash scenario design closing two right lanes (lanes 3 and 4 with exit ramp open). This figure depicts six banks of four active traffic management (ATM) signs with a changeable message sign (CMS) on the gantry to the right over a four-lane road with exit lanes on the right. The figure shows an example of ATM sign operation with a crashed vehicle and an emergency vehicle in the two right lanes between the fourth and fifth banks of ATM signs. The specific layout bottom to top (i.e., the direction of travel) is as follows:

• From left to right, the first bank of signs shows a high occupancy vehicle (two passengers) restriction sign (HOV 2), normal operations, normal operations, and a lane closure 1 mi ahead. The CMS shows "RIGHT LANES EXIT ONLY."
• From left to right, the second bank of signs shows "OPEN TO ALL," normal operations, a lane closure 1 mi ahead, and merge left. The CMS shows "RIGHT LANES EXIT ONLY."
• From left to right, the third bank of signs shows "OPEN TO ALL," normal operations, merge left, and lane closed. The CMS shows "RIGHT LANES EXIT ONLY."
• From left to right, the fourth bank of signs shows: "OPEN TO ALL," normal operations, and the two right lanes closed. The CMS shows "RIGHT LANES EXIT ONLY."
• The fifth bank of signs shows a speed limit of 65 mi/h on four lanes. The CMS shows "END REDUCE SPEED ZONE."
• From left to right, the sixth bank of signs shows high-occupancy vehicle (HOV)-2 and normal operations in the three left lanes. The CMS is blank.

Back

Figure 55. Illustration. Design of scenario 5-slow-moving traffic in all lanes. This figure depicts six banks of active traffic management (ATM) signs with a changeable message sign (CMS) on the right gantry over a four-lane road. The figure shows an example of ATM sign operation with slow-moving traffic. The specific layout bottom to top (i.e., the direction of travel) is as follows:

• The first bank of signs shows a high-occupancy vehicle (HOV) (two passengers) restriction sign (HOV-2) in the left lane, and the other three signs are blank. The CMS shows "REDUCE SPEED ZONE AHEAD."
• The second bank of signs shows a speed limit of 60 mi/h in the left lane and a speed limit of 50 mi/h in the other three lanes. The CMS shows "REDUCE SPEED ZONE."
• The third bank of signs shows a speed limit of 50 mi/h in the left lane and a speed limit of 40 mi/h in the other three lanes. The CMS shows "REDUCE SPEED ZONE."
• The fourth bank of signs shows a speed limit of 45 mi/h in the left lane and a speed limit of 35 mi/h in the other three lanes. The CMS shows "REDUCE SPEED ZONE."
• The fifth bank of signs shows a speed limit of 65 mi/h in all four lanes. The CMS shows "END REDUCE SPEED ZONE."
• The sixth bank of signs shows HOV-2 in the left lane and the other three signs blank. The CMS is blank.

Back

Figure 60. Graph. Speed profile for scenario 5a (first speed reduction). This figure shows a graph of the speed profile for scenario 5a (the first speed reduction). Three lines are shown: mean speed, 50th percentile speed, and 85th percentile speed. Speed is on the y-axis from 30 to 70 mi/h, and distance from the start of the scenario is on the x-axis from 0 to 3,000 m. The following speed limits were defined for the scenario:

• 65 mi/h for 0 to 800 m.
• 50 mi/h for 800 to 1,600 m.
• 40 mi/h for 1,600 to 2,400 m.
• 35 mi/h for 2,400 to 3,200 m.
• 65 mi/h for 3,200 to 3,500 m.

The 85th percentile plot started at 65 mi/h for the first 800 m, slows to 49 mi/h from 800 to 1,600 m, slows to 40 mi/h from 1,600 to 2,400 m, slows to 38 mi/h from 2,400 to 3,200 mi/h, and then accelerates to 56 mi/h from 3,200 to 3,500 m. The 50th percentile and mean speed plots decelerate from at 64 to 61 mi/h in the first 800 m, slow to 52 mi/h from 800 to 1,600 m, slow to 42 mi/h from 1,600 to 2,400 m, slow to 38 mi/h from 2,400 to 3,200 mi/h, and then accelerate to 50 mi/h from 3,200 to 3,500 m. (1 mi/h = 1.61 km/h and 1 ft = 0.305 m)

Back

Figure 79. Graph. Speed profile for scenario 2 (stalled vehicle). This figure shows a graph of the speed profile for scenario 2 (stalled vehicle). Three lines are shown: mean speed, 50th percentile speed, and 85th percentile speed in a 65-mi/h posted speed limit road during a scenario with a stalled vehicle. The y-axis shows speed from 30 to 70 mi/h, and the x-axis plots the distance from the start of the scenario. The following speed limit limits were defined for the scenario:

• 40 mi/h for 0 to 800 m.
• 35 mi/h for 800 to 4,000 m.
• 65 mi/h for 4,000 to 4,800 m.

The 85th percentile plot started at 67 mi/h, decelerated to 42 mi/h at 1,200 m, and then accelerated back to 67 mi/h from 1,200 to 4,800 m. The 50th percentile plot started 64 mi/h, decelerated to 37 mi/h at 1,200 m, and then accelerated to 64 mi/h from 1,200 to 4,800 m. The mean speed plot started at 64 mi/h, decelerated to 40 mi/h at 1,200 m, and then accelerated to 64 mi/h from 1,200 to 4,800 m. (1 mi/h = 1.61 km/h and 1 ft = 0.305 m)

Back

Figure 80. Speed profile for scenario 3 (two left lanes closed). This figure shows a graph of the speed profile for scenario 3 (two left lanes closed. Three lines are shown: the mean speed, 50th percentile speed, and 85th percentile speed in a 65 mi/h posted speed limit road during a scenario with two left lanes closed. The y-axis shows speed from 30 to 70 mi/h, and the x-axis plots the distance in meters from the start of the scenario. The following speed limits were defined for the scenario:

• 40 mi/h for 0 to 800 m.
• 35 mi/h for 800 to 4,000 m.
• 65 mi/h for 4,000 to 4,800 m.

The 85th percentile plot started at 66 mi/h, decelerates=d to 41 mi/h at 1,600 ft, and then accelerated back to 67 mi/h from 1,600 to 4,800 m. The 50th percentile plot started 63 mi/h, decelerated to 39 mi/h at 1,600 m, and then accelerates=d to 64 mi/h from 1,600 to 4,800 m. The mean speed plot started at 63 mi/h, decelerated to 40 mi/h at 1,600 m, and then accelerated to 64 mi/h from 1,600 to 4,800 m. (1 mi/h = 1.61 km/h and 1 ft = 0.305 m)

Back

Figure 81. Graph. Speed profile for scenario 4 (two right lanes blocked, take exit). This figure shows a graph of the speed profile for scenario 4 (two right lanes blocked, take exit). Three lines are shown: the mean speed, 50th percentile speed, and 85th percentile speed in a 65 mi/h posted speed limit road during a scenario with two right lanes closed and an exit ramp. The y-axis shows speed from 30 to 70 mi/h, and the x-axis plots the distance in meters from the start of the scenario. The following speed limits were defined for the scenario:

• 40 mi/h for 0 to 800 m.
• 35 mi/h for 800 to 3,200 m.

The 85th percentile plot started at 66 mi/h, decelerated to 44 mi/h at 1,000 m, and then accelerated back to 58 mi/h from 1,000 to 3,200 m. The 50th percentile plot started 63 mi/h, decelerated to 38 mi/h at 1,400 m, and then accelerated to 64 mi/h from 1,600 to 4,800 m. The mean speed plot started at 63 mi/h, decelerated to 40 mi/h at 1,600 m, and then accelerated to 64 mi/h from 1,600 to 4,800 m. (1 mi/h = 1.61 km/h and 1 ft = 0.305 m)

Back

Figure 82. Graph. Speed profile for scenario 5a (first speed reduction). This figure shows a graph of the speed profile of scenario 5a (first speed reduction). Three lines are shown: mean speed, 50th percentile speed, and 85th percentile speed in a 65 mi/h posted speed limit road during a scenario with two right lanes closed and an exit ramp. The y-axis shows speed from 30 to 70 mi/h, and the x-axis plots the distance in meters from the start of the scenario. The following speed limits were defined for the scenario:

• 65 mi/h for 0 to 1,600 m.
• 50 mi/h for 1,600 to 2,400 m.
• 40 mi/h for 2,400 to 3,200 m.
• 35 mi/h for 3,200 to 4,000 m.
• 65 mi/h for 4,000 to 4,800 m.

The 85th percentile plot remained steady at 67 mi/h from 0 to 1,600 m, decelerated to 40 mi/h from 1,600 to 3,800 m, and then accelerated back to 59 mi/h from 3,800 to 4,800 m. The 50th percentile plot remained steady at 65 mi/h from 0 to 1,600 m, decelerated to 38 mi/h from 1,600 to 4,000 m, and then accelerated back to 56 mi/h from 1,600 to 4,800 m. The mean speed plot remained steady at 65 mi/h from 0 to 1.600 m, decelerated to 36 mi/h from 1,600 to 4,000 m, and then accelerated back to 56 mi/h from 1,600 to 4,800 m. (1 mi/h = 1.61 km/h and 1 ft = 0.305 m)

Back