Evaluation of The TAPCO Sequential Dynamic Curve Warning System

SPEED ANALYSIS

This chapter describes the speed metrics used to assess the effectiveness of the SDCWS. Since data were collected at three locations per curve, results for individual sites are summarized.

Speed Metrics

The change in speed from the before period was compared to each after period. A negative result indicates that speeds were reduced from the before period to the after period. A positive value indicates that speed increased from the before period to the after period. Mean and 85th percentile speeds are shown sing a trend line. This is shown for graphical purposes only and should not be interpreted to indicate that speeds can be interpolated between data collection periods.

The change in mean and 85th percentile speed from the before period speed to specific after period speed are shown in miles per hour (mph). The percentage change in the fraction of vehicles exceeding the posted or advisory speed is also presented. A number of speed metrics were calculated for the direction of travel towards the signs. They include average speed, standard deviation (SD) of speed, 50th percentile speed, 85th percentile speed, and number of vehicles traveling 5, 10, 15, or 20 mph over the posted or advisory speed limit. For simplicity in setting up the pneumatic road tubes, the traffic counters were set up to record both directions of traffic on the two-way roadway. Results were reduced by lane and are only presented for traffic traveling in the direction of the SDCWS.

Results to Date

This interim report does not provide a commentary on the results to date. Tables 5 and 6 provide a summary of speed statistics across all sites at both PC and CC. The table shows the changes from before to 1 month after, with a negative sign showing a reduction in speed or percentage. Appendix contains the full data set collected before installation and 1 month after installation, in both tabular and graphic formats. The schedule of the data collection for each State is provided in table 7. This shows both data that have been collected and what will be collected in the future.

Table 5. Summary of results at point of curvature after 1 month.
State		IA	MO	TX				WA			WI
Road		Hwy 144	Hwy 221	FM 109	FM 407	FM 530	FM 1488	SR 7	SR 9	SR 203	Hwy 20	Hwy 67	Hwy 213
Posted Speed		55	55	60	55	60	55	50	55	55	55	55	55
Curve Advisory Speed		45	40	35	40	-0.9	40	20	40	None	30	25	50
Change in mean speed (mph)		-1.5	-1.5	-0.8	-1.8	-2	-2.4	-2.8	-1.4	-2	-1.8	-1.6	-0.7
Change in 85th percentile speed(mph)		-1	-1	-1	-2	-2.6	-3	-3	-1	-2	-2	-1	0
Change in Fraction of vehicles exceeding posted or advisory speed by	5 mph	-19.7%	-6.4%	-2.2%	-6.7%	-20.3%	-8.5%	-7.3%	-30.4%	-2.1%	-9.1%	0.0%	-9.5%
	10 mph	-33.3%	-17.1%	-8.8%	-20.9%	-36.4%	-27.1%	-30.0%	-50.0%	-14.5%	-19.0%	-3.1%	-25.0%
	15 mph	0.0%	-32.0%	-23.3%	-41.9%	-63.6%	-53.6%	-51.4%	-100.0%	-46.5%	-40.7%	-8.0%	0.0%
	20 mph	0.0%	-50.0%	0.0%	0.0%	0.0%	0.0%	-77.8%	0.0%	-62.5%	-57.1%	-21.5%	0.0%

Table 6. Summary of results at center of curve after 1 month.
State		IA	MO	TX				WA			WI
Road		Hwy 144	Hwy 221	FM 109	FM 407	FM 530	FM 1488	SR 7	SR 9	SR 203	Hwy 20	Hwy 67	Hwy 213
Posted Speed		55	55	60	55	60	55	50	55	55	55	55	55
Curve Advisory Speed		45	40	35	40	35	40	20	40	None	30	25	50
Change in mean speed (mph)		-2.1	0.3	-1.4	-1.1	-2	-0.1	-1.4	-0.9	-0.1	-1.8	-1.8	-1
Change in 85th percentile speed (mph)		-2	0	-2	-2	-2.6	0	-1	-1	0	-2	-2	-1
Change in fraction of vehicles exceeding posted or advisory speed by	5 mph	-38.1%	0.0%	-5.7%	-8.2%	-20.3%	-4.8%	-19.0%	-26.3%	0.0%	-18.2%	-2.1%	-11.9%
	10 mph	-58.3%	10.5%	-27.7%	-29.7%	-36.4%	2.5%	-45.0%	-33.3%	-2.8%	-45.5%	-11.6%	-20.0%
	15 mph	0.0%	28.6%	-51.4%	-60.0%	-63.6%	0.0%	0.0%	0.0%	-4.0%	-66.7%	-28.3%	50.0%
	20 mph	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	0.0%	-100.0%	-46.7%	0.0%

Table 7. Schedule of activities, all sites.
Activity Description	Schedule (Week)	Status
*Before data collection*		Complete
Washington	7/17/2012
Wisconsin	5/21 2012
Missouri	6/13 2012
Texas	6/25 and 7/9 2012
Iowa	8/29 2013
*Installation*		Complete
Washington	8/1/2012
Wisconsin	6/11 2012
Missouri	6/25 2012
Texas	7/16/2012
Iowa	9/10 2012
*1-month after data collection*		Complete
Washington	9/12/2012
Wisconsin	7/9 2012
Missouri	8/1 2012
Texas	9/3, 9/10,/9/24 2012
Iowa	10/10 2012
*12-month after data collection*
Washington	August 2013
Wisconsin	June 2013
Missouri	July 2013
Texas	June/July 2013
Iowa	September 2013
*18-month after data collection*
Washington	February 2014
Wisconsin	December 2013
Missouri	January 2014
Texas	December 2013/January 2014
Iowa	March 2014
*Before Crash data collection*
Washington	April 2013
Wisconsin	May 2013
Missouri	February 2013
Texas	TBD
Iowa	February 2013
*After Crash data collection*
Washington	April 2014
Wisconsin	May 2014
Missouri	September 2013
Texas	TBD
Iowa	February 2014
*First Year Evaluation*	12/31/2013
*Final Report*	8/31/2014

Appendix A. Baseline Data For each Test Section

Hwy 144(IA) - Eastbound Before

Composite image: Iowa Highway 144 eastbound before implementation, showing table data pointing to map for counter number, direction, start time, end time, and duration stopwatch for upstream, point of curvature, and center of curve

Figure 16. Photo. Iowa Highway 144 before data collection.

Hwy 144(IA) - Eastbound 1 Month After

Composite image: Iowa Highway 144 eastbound 1 month after implementation, showing table data pointing to map for counter number, direction, start time, end time, and duration stopwatch for upstream, point of curvature, and center of curve

Figure 17. Photo. Iowa Highway 144 1 month after data collection.

Hwy 144(IA) - Eastbound

Map: Iowa Highway 144 site layout showing locations of no passing sign and curve warning sign before curve on opposite sides of the road

Figure 18. Photo. Iowa Highway 144 site layout.

Iowa 144
Date: 8/29-8/30/2012
Period: Before

	location (gps at center of curve)
2-12' lanes	# lanes and width
Left	curve direction (left or right)
Gravel 4'	shoulder type and width
45	posted speed of curve in each direction
55	tangent speed in each direction
55	advisory speed in each direction
See below	grade (average of 3 readings and list if positive or negative)
See below	super elevation
See Layout	location and type of signing before and in the
Asphalt	pavement type and condition
None	presence and location of street lighting

Grade	Begin S-N				Center W-E				End W-E
	EB	Center	WB	Average	EB	Center	WB	Average	EB	Center	WB	Average
	-.4	-.1	-.2	-.23	-0	-.9	-.4	-.43	-.6	-.5	-.8	-.63

Super Elevation	Begin W-E				Center S-N				End S-N
	EB	Center	WB	Average	EB	Center	WB	Average	EB	Center	WB	Average
	-5.3	-3.7	-4.9	-4.63	-8.5	-7.1	-7.4	-7.67	-1.2	+1	-1.4	-.53

Figure 19. Chart. Iowa Highway 144 site information.

Hwy 221 (MO) - Northbound Before

Composite image: Missouri Highway 221 northbound before implementation, showing table data pointing to map for counter number, direction, start time, end time, and duration stopwatch for upstream, point of curvature, and center of curve

Figure 20. Photo. Missouri Highway 221 before data collection.

Hwy 221 (MO) - Northbound 1 Month After

Composite image: Missouri Highway 221 northbound 1 month after implementation, showing table data pointing to map for counter number, direction, start time, end time, and duration stopwatch for upstream, point of curvature, and center of curve

Figure 21. Photo. Missouri Highway 221 1 month after data collection.

Hwy 221 (MO) - Northbound

Map: Missouri Highway 221 site layout showing curve warning with advisory speed southbound between the second and third chevron, a driveway in the study direction directly before the curve, and a curve warning with advisory 40 mile per hour speed in the study direction

Figure 22. Photo. Missouri Highway 221 site layout.

Missouri 221
Date: 6/13-6/1/2012
Period: Before

N42^°31.432' W088^°58.944'	location (gps at center of curve)
2 Lanes, 22' Asphalt	# lanes and width
Right	curve direction (left or right)
4' Asphalt Right 4' +3' Asphalt Left sharp drop	shoulder type and width
55	posted speed of curve in each direction
55	tangent speed in each direction
40	advisory speed in each direction
See Below	grade (average of 3 readings and list if positive or negative)
See Below	super elevation
See Layout	location and type of signing before and in the
Asphalt, Good	pavement type and condition
None	presence and location of street lighting

Grade	Begin S-N				Center S-N				End W-E
	NB	Center	SB	Average	NB	Center	SB	Average	NB	Center	SB	Average
	-3.6	-3.3	-2.9	-3.27	-4.5	-4.4	-4.7	-4.53	-8.8	-9.1	-9.8	-9.23

Super Elevation	Begin W-E				Center S-N				End S-N
	NB	Center	SB	Average	NB	Center	SB	Average	NB	Center	SB	Average
	-4.2	-2.6	-1.2	-2.67	-8.6	-8.0	-6.0	-7.53	2.0	-0.7	-1.4	-.03

Figure 23. Chart. Missouri Highway 221 site information.

Washington SR9
Date 7/17 - 7/18, 2012
Period: Before

Composite image: Washington State Route 9 before implementation, showing table data pointing to map for counter number, direction, start time, and end time for upstream, point of curvature, and center of curve

Figure 24. Map. Washington State Route 9 before data collection

Washington SR9
Date 9/12 - 9/13, 2012
Period: 1 Month After

Composite image: Washington State Route 9 1 month after implementation, showing table data pointing to map for counter number, direction, start time, and end time for upstream, point of curvature, and center of curve

Figure 25. Map. Washington State Route 9 1 month after data collection.

Washington SR 9
Date: 7/17-7/18/2012
Period: Before

	location (gps at center of curve)
2 Lanes, 10' Each CL Rumble 12" Wide	# lanes and width
Left	curve direction (left or right)
2' Asphalt Shoulder Both	shoulder type and width
50	posted speed of curve in each direction
50	tangent speed in each direction
40	advisory speed in each direction
See Below	grade (average of 3 readings and list if positive or negative)
See Below	super elevation
See Layout	location and type of signing before and in the
Asphalt	pavement type and condition
None	presence and location of street lighting

Figure 26. Chart. Washington State Route 9 site information.

Washington SR9
Date 7/17 - 7/18, 2012
Period: Before

Composite image: Washington State Route 203 before implementation, showing table data pointing to map for counter number, direction, start time, and end time for upstream, point of curvature, and center of curve

Figure 27. Map. Washington State Route 203 before data collection.

Washington SR203
Date 9/12 - 9/13, 2012
Period: 1 Month After

Composite image: Washington State Route 203 1 month after implementation, showing table data pointing to map for counter number, direction, start time, and end time for upstream, point of curvature, and center of curve

Figure 28. Map. Washington State Route 203 1 month after data collection

	location (gps at center of curve)
2 lanes with 12" CL Rumble, 11' NB Lane; 10.5' SB Lane	# lanes and width
Left	curve direction (left or right)
NB-4.5' Asphalt Shld SB-8' Asphalt w/ 12" Rumble	shoulder type and width
55	posted speed of curve in each direction
55	tangent speed in each direction
None	advisory speed in each direction
See Below	grade (avg. of 3 readings and list if positive or negative)
See Below	super elevation
See Layout	location and type of signing before and in the
Asphalt	pavement type and condition
None	presence and location of street lighting

Figure 29. Chart. Washington State Route 203 site information

Washington SR7
Date 7/17 - 7/18, 2012
Period: Before

Composite image: Washington State Route 7 before implementation, showing table data pointing to map for counter number, direction, start time, and end time for upstream, point of curvature, and center of curve

Figure 30. Map. Washington State Route 7 before data collection.

Washington SR7
Date 9/12 - 9/13, 2012
Period: 1 Month After

Composite image: Washington State Route 7 1 month after implementation, showing table data pointing to map for counter number, direction, start time, and end time for upstream, point of curvature, and center of curve

Figure 31. Photo. Washington State Route 7 1 month after data collection.

Washington SR 7
Date: 7/17-7/18/2012
Period: Before

	location (gps at center of curve)
2 Lane with 12" Rumble NB 11' Lane; SB 10' Lane	# lanes and width
Right	curve direction (left or right)
Paved	shoulder type and width
50	posted speed of curve in each direction
50	tangent speed in each direction
20	advisory speed in each direction
See Below	grade (average of 3 readings and list if positive or negative)
See Below	super elevation
See Layout	location and type of signing before and in the
Asphalt, Good	pavement type and condition
None	presence and location of street lighting

Figure 32. Chart. Washington State Route 7 site information.

Wisconsin 213
Date 5/21 - 5/22, 2012
Period: Before

Composite image: Wisconsin Highway 213 southbound before implementation, showing table data pointing to map for upstream, point of curvature, and center of curve

Figure 33. Map. Wisconsin Highway 213 before data collection.

Wisconsin 213
Date 5/21 - 5/22, 2012
Period: Before

Composite image: Wisconsin Highway 213 southbound 1 month after implementation, showing table data pointing to map for upstream, point of curvature, and center of curve

Figure 34. Map. Wisconsin Highway 213 1 month after data collection.

Wisconsin 213
Date 5/21 - 5/22, 2012
Period: Before

Map: Wisconsin Highway 213 site layout showing relative locations of curve warning with advisory speed, intersection sign, driveway, and left arrow sign approaching the curve

Figure 35. Map. Wisconsin Highway 213 site layout.

Wisconsin 213
Date: 5/21-5/22/2012
Period: Before

N42^°35.977' W089^°12.570'	location (gps at center of curve)
2 Lanes, 24'	# lanes and width
Left	curve direction (left or right)
3' Asphalt with varying gravel edge	shoulder type and width
55	posted speed of curve in each direction
55	tangent speed in each direction
50	advisory speed in each direction
Below	grade (average of 3 readings and list if positive or negative)
Below	super elevation
Previous Slide (5 Chevrons)	location and type of signing before and in the
Asphalt, Good	pavement type and condition
None	presence and location of street lighting

Grade	Begin W-E				Center W-E				End W-E
	SB	Center	NB	Average	SB	Center	NB	Average	SB	Center	NB	Average
	-4.9	-4.9	-4.8	-4.87	-5.6	-5.4	-5.7	-5.57	-3.8	-3.2	-3.1	-3.37

Super Elevation	Begin S-N				Center S-N				End S-N
	SB	Center	NB	Average	SB	Center	NB	Average	SB	Center	NB	Average
	-3.8	-3.5	-4.7	-4.00	-6.5	-7.1	-8.6	-7.40	-4.6	-4.8	-5.4	-4.93

Figure 36. Chart. Wisconsin Highway 213 site information.

Wisconsin 20
Date 5/21 - 5/22, 2012
Period: Before

Composite image: Wisconsin Highway 20 westbound before implementation, showing table data pointing to map for upstream, point of curvature, and center of curve

Figure 37. Map. Wisconsin Highway 20 before data collection.

Wisconsin 20
Date 7/9 - 7/10, 2012
Period: 1 Month After

Composite image: Wisconsin Highway 20 westbound 1 month after implementation, showing table data pointing to map for upstream, point of curvature, and center of curve

Figure 38. Map. Wisconsin Highway 20 1 month after data collection.

Wisconsin 20
Date 5/21 - 5/22, 2012
Period: Before

Map: Wisconsin Highway 20 site layout showing relative positions of heavy trucks pulling in and out, watch for backups with railroad below, curve warnings with advisory speeds, three-leg intersection sign, Honey Creek Road left sign, railroad crossing sign and pavement markings right before point of curvature, left turn sign between the third and fourth chevrons, and railroad crossing sign

Figure 39. Map. Wisconsin Highway 20 site layout.

Wisconsin 20
Date: 5/21-5/22/2012
Period: Before

N42^o46.212' W088^o18.078'	location (gps at center of curve)
2 Lanes, 25'	# lanes and width
Right	curve direction (left or right)
South (2' Asphalt, 6' gravel) North(14' Asphalt w/Drainage	shoulder type and width
55	posted speed of curve in each direction
55	tangent speed in each direction
30	advisory speed in each direction
See Below	grade (average of 3 readings and list if positive or negative)
See Below	super elevation
See Layout (9 Chevrons)	location and type of signing before and in the curve
Asphalt, Good	pavement type and condition
None	presence and location of street lighting

Grade	Begin W-E				Center W-E				End S-N
	SB	Center	NB	Average	SB	Center	NB	Average	SB	Center	NB	Average
	3	3	2.5	2.83	7.3	7	7.2	7.17	-5.9	-6.4	-6.5	-6.27

Super Elevation	Begin S-N				Center S-N				End W-E
	SB	Center	NB	Average	SB	Center	NB	Average	SB	Center	NB	Average
	-4	-5.3	-3	-4.10	-7.7	-8.3	-8.2	-8.07	-3.4	-5.6	-4	-4.33

Figure 40. Chart. Wisconsin Highway 20 site information.

Wisconsin 67
Date 5/21 - 5/22, 2012
Period: Before

Composite image: Wisconsin Highway 67 before implementation, showing table data pointing to map for upstream, point of curvature, and center of curve

Figure 41. Map. Wisconsin Highway 67 before data collection.

Wisconsin 67
Date 7/9-7/10 2012
Period: 1 Month After

Composite image: Wisconsin Highway 67 1 month after implementation, showing table data pointing to map for upstream, point of curvature, and center of curve

Figure 42. Map. Wisconsin Highway 67 1 month after data collection.

Wisconsin 67
Date 5/21-5/22 2012
Period: Before

Map: Wisconsin Highway 67 site layout showing relative locations of passing lane northbound, three curve warnings with advisory speeds, and guardrail on south side through curve

Figure 43. Map Wisconsin Highway 67 site layout.

Wisconsin 67
Date: 5/21-5/22/2012
Period: Before

N42^o56.244' W088^o28.056'	location (gps at center of curve)
2 Lanes, 24'	# lanes and width
Right	curve direction (left or right)
South (3.5' asphalt w/4' Gravel then guardrail through curve) North (1.5' asphalt w/ 3' gravel)	shoulder type and width
55	posted speed of curve in each direction
55	tangent speed in each direction
25	advisory speed in each direction
See Below	grade (average of 3 readings and list if positive or negative)
See Below	super elevation
See Layout(5 Chevrons)	location and type of signing before and in the curve
Asphalt, good	pavement type and condition
None	presence and location of street lighting

Grade	Begin W-E				Center W-E				End S-N
	SB	Center	NB	Average	SB	Center	NB	Average	SB	Center	NB	Average
	-1.6	-1.7	-1.9	-1.73	-0.1	-0.12	-0.2	-0.14	0.7	0.6	1	0.77

Super Elevation	Begin S-N				Center S-N				End W-E
	SB	Center	NB	Average	SB	Center	NB	Average	SB	Center	NB	Average
	2	1.1	-0.4	0.90	5.8	5.2	5.1	5.37	3.6	3.2	3.1	3.30

Figure 44. Chart. Wisconsin Highway 67 site information.