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Publication Number: FHWA-HRT-05-054
Date: September 2005

Quantification of Smoothness Index Differences Related To Long-Term Pavement Performance Equipment Type

Appendix B: Profiler Verification Studies

1996 VERIFICATION TEST

In 1996, FHWA purchased four K.J. Law Engineers T-6600 profilers to replace the K.J. Law Engineers DNC 690 profilers that were used in the LTPP program. Each region compared the DNC 690 and T-6600 profilers before using the T-6600 profiler to collect profile data for the LTPP program.

Each region used four test sections for the verification test; each test section was 152.4 m (500 ft) long. Two sections were surfaced with AC, while the other two were jointed PCC pavements. When selecting the test sections, the aim was to select two sections for each pavement type so that one section will have an IRI value of less than 1.6 m/km (101 inches/mi), and the other section will have an IRI value of greater than 2.2 m/km (139 inches/mi). Dipstick measurements were performed on both wheelpaths at all four test sections. Each profiler performed three measurement sequences at each test section, with one measurement sequence being performed on 1 day. A measurement sequence consisted of obtaining a set of profile runs (a minimum of five good profile runs) on a test section at test speeds of 64 and 80 km/h (40 and 50 mi/h). Therefore, at each section, each profiler collected six data sets (two speeds x three sequences). During testing, each profiler collected 24 data sets (4 test sections x 2 test speeds x 3 measurement sequences). The wheelpaths at the test sections were not marked, and the profiler drivers judged the location of the wheelpath when profiling the sections.

The guidelines for testing recommended that concurrent measurements be made at the test sections with the two profilers with a minimum time lag between measurements. The guidelines also recommended that an effort should be made to obtain the three profiler measurement sequences for a test section on 3 consecutive days. Each RSC was asked to compute the IRI value of the profiler data and Dipstick data using ProQual. The bias in the IRI value of a profiler for a wheelpath on a test section was determined by computing the difference between the average profiler IRI at a specific speed for a data set (computed by averaging the IRI values obtained from replicate runs) and the Dipstick IRI. The profiler was deemed to have satisfied the IRI bias criterion if this difference in IRI was within ±0.16 m/km (±10 inches/mi). For each data set, the standard deviation of the IRI for each wheelpath was computed by using the IRI values obtained for the replicate profile runs. The precision of the profiler was evaluated by using this standard deviation of the IRI. The profiler was deemed to have satisfied the precision criterion if the standard deviation of the IRI was less than 0.04 m/km (2.5 inches/mi).

Each RSC prepared a report documenting the results of this comparison test. (See references 24, 25, 26, and 27.) A summary of the findings contained in these reports is presented separately for the four regions.

North Atlantic Region

For all profiler testing, the same driver operated each profiler. A review of the report indicated that, in many cases, more than five repeat runs were conducted for each data set. Thereafter, five runs were selected for computing the average IRI and the standard deviation of the IRI. It appears that the five runs were selected after the IRI values from all available runs were reviewed to select values that were similar to each other. The average profiler IRI values obtained for the 80-km/h (50-mi/h) profiler runs and IRI obtained from the Dipstick measurements at the four sites that were extracted from the report are presented in table 46. The differences between the average profiler IRI and the Dipstick IRI for the profile runs obtained at 80 km/h (50 mi/h) are presented in table 47. It should be noted that testing resulted in six data sets at each section, and these tables only show the results obtained for 80-km/h (50-mi/h) testing, which comprise three data sets from a test section.

 

Table 46. Profiler IRI for 80-km/h (50-mi/h) runs and Dipstick IRI: North Atlantic region.
Site Sequence Test Date Average IRI (m/km)
Left Wheelpath Right Wheelpath
T-6600 DNC 690 Dipstick T-6600 DNC 690 Dipstick
Smooth AC 1 10/07/96 0.78 0.86 0.83 0.89 0.87 0.92
2 10/09/96 0.74 0.86   0.88 0.86  
3 10/10/96 0.75 0.87 0.87 0.86
Rough AC 1 10/07/96 2.44 2.26 2.30 1.92 1.89 1.91
2 10/09/96 2.11 2.27   1.67 1.92  
3 10/10/96 2.28 2.28 1.72 1.87
Smooth PCC 1 10/03/96 1.19 1.25 1.27 1.37 1.30 1.39
2 10/04/96 1.18 1.22   1.34 1.31  
3 10/04/96 1.20 1.21 1.40 1.33
Rough PCC 1 10/07/96 1.92 1.81 1.93 2.11 2.12 2.22
2 10/09/96 1.88 1.89   2.23 2.15  
3 10/10/96 1.88 1.88 2.18 2.18
Note: Only one data set was obtained for Dipstick at each site.

1 m/km = 5.28 ft/mi

 

Table 47. Differences between the profiler IRI and the Dipstick IRI: North Atlantic region.
Site Sequence Test Date Average IRI (m/km)
Left Wheelpath Right Wheelpath
T-6600 DNC 690 T-6600 DNC 690
Smooth AC 1 10/07/96 -0.05 0.03 -0.03 -0.05
2 10/07/96 -0.09 0.03 -0.05 -0.06
3 10/10/96 -0.08 0.04 -0.05 -0.06
Rough AC 1 10/07/96 0.14 -0.04 0.01 -0.02
2 10/07/96 -0.20 -0.04 -0.24 0.00
3 10/10/96 -0.02 0.02 -0.20 -0.05
Smooth PCC 1 10/03/96 0.08 -0.02 -0.03 -0.09
2 10/04/96 -0.09 -0.05 -0.07 0.04
3 10/04/96 -0.07 0.06 -0.08 -0.06
Rough PCC 1 10/07/96 0.08 0.20 -0.01 0.05
2 10/09/96 0.11 0.15 -0.06 -0.02
3 10/10/96 0.08 0.19 0.01 0.01

1 m/km = 5.28 ft/mi

The findings from the study are:

  • Both profilers passed the IRI bias criterion for all data sets, except for the followin cases: (1) at the rough AC site, the T-6600 profiler failed the criterion for two both the left and right wheelpaths, and (2) the DNC 690 profiler failed the criterion at the rough PCC site along the right wheelpath for one data set.
  • Both profilers passed the precision criterion for all data sets, except for the following cases: (1) at the rough AC site, the DNC 690 profiler failed the criterion for two data sets in the right wheelpath; the T-6600 profiler failed the criterion along the left wheelpath for four data sets and along the right wheelpath for three data sets, and (2) at the rough PCC site, the DNC 690 profiler failed the criterion for two data sets in the right wheelpath; the T-6600 profiler failed the criterion along the right wheelpath for three data sets.
  • For both profilers, it was found that the IRI values for both the left and right wheelpaths were insensitive to the two testing speeds. This held true for both smooth and rough pavements, as well as for AC and PCC surfaces.
  • For most cases, the IRI values obtained by the profilers were less than those obtained by Dipstick
  • The IRI values varied much more for the rough sections when compared to the smooth sections. The majority of these occurrences involved the T-6600 profiler. Overall, the IRI values obtained from the DNC 690 profiler appeared to be more repeatable than those obtained from the T-6600 profiler. This might have been the result of the T-6600 profiler being operated by an inexperienced driver who was not as skilled at consistently tracking the wheelpath as the driver of the DNC 690 profiler.

North Central Region

For all profiler testing, the same drivers operated each profiler. The drivers of both profilers used a camera system to help them align the vehicle along the right wheelpath. The DNC 690 and the T-6600 profilers had different sensor spacings (1,676 and 1,422 mm (66 and 56 inches), respectively).

The report indicated that the first five acceptable runs obtained at a section for each data set were used to compute the average IRI and standard deviation of the IRI for each wheelpath. The average profiler IRI values obtained for the 80-km/h (50-mi/h) profiler runs and IRI obtained from the Dipstick measurements at the four sites that were extracted from the report are presented in table 48. The differences between the average profiler IRI and the Dipstick IRI for the profiler runs obtained at 80 km/h (50 mi/h) are presented in table 49. It should be noted that testing resulted in six data sets at each section, and these tables only show the results obtained for the 80-km/h (50-mi/h) testing, which comprise three data sets from a test section.

 

Table 48. Profiler IRI for 80-km/h (50-mi/h) runs and Dipstick IRI: North Central region
Site Sequence Test Date Average IRI (m/km)
Left Wheelpath Right Wheelpath
T-6600 DNC 690 Dipstick T-6600 DNC 690 Dipstick
Smooth AC 1 10/07/96 1.07 1.00 0.98 1.12 1.05 1.08
2 10/09/96 1.05 1.01   1.05 1.07  
3 10/10/96 1.02 1.00 1.08 1.05
Rough AC 1 10/07/96 3.94 3.95 3.82 4.73 4.98 4.86
2 10/09/96 3.96 3.97   4.78 4.92  
3 10/10/96 3.94 3.95 4.79 4.90
Smooth PCC 1 10/03/96 1.11 1.11 1.05 1.07 1.09 1.15
2 10/04/96 1.11 1.10   1.08 1.07  
3 10/04/96 1.11 1.11 1.08 1.09
Rough PCC 1 10/07/96 2.64 2.75 2.55 3.00 3.06 3.01
2 10/09/96 2.67 2.70   2.95 2.99  
3 10/10/96 2.63 2.74 3.02 3.02
Note: Only one data set was obtained for Dipstick at each site.

1 m/km = 5.28 ft/mi

Table 49. Differences between the profiler IRI and the Dipstick IRI: North Central region
Site Sequence Test Date Average IRI (m/km)
Left Wheelpath Right Wheelpath
T-6600 DNC 690 T-6600 DNC 690
Smooth AC 1 10/07/96 0.09 0.03 0.04 -0.03
2 10/07/96 0.07 0.04 -0.04 -0.01
3 10/10/96 0.05 0.02 0.00 -0.03
Rough AC 1 10/07/96 0.12 0.13 -0.12 -0.12
2 10/07/96 0.15 0.15 -0.07 0.07
3 10/10/96 0.12 0.14 -0.07 -0.04
Smooth PCC 1 10/03/96 0.06 0.05 -0.08 -0.06
2 10/04/96 0.06 0.05 -0.08 0.04
3 10/04/96 0.06 0.04 -0.07 -0.06
Rough PCC 1 10/07/96 0.08 0.20 -0.01 0.05
2 10/09/96 0.11 0.15 -0.06 -0.02
3 10/10/96 0.08 0.19 0.01 0.01

1 m/km = 5.28 ft/mi

The findings from the study are:

  • Both profilers satisfied the IRI bias criterion along both wheelpaths on the smooth AC and smooth PCC sections. On the rough AC section, the DNC 690 profiler passed the bias criterion for both wheelpaths for all of the cases, while the T-6600 profiler failed the bias criterion along the left wheelpath for all data sets. On the rough PCC section, the DNC 690 profiler failed the bias criterion for four data sets along the left wheelpath, while the T-6600 profiler passed the bias criterion for all of the cases along both wheelpaths.
  • Both profilers satisfied the IRI precision criterion along both wheelpaths on the smooth AC and smooth PCC sections. On the rough AC section, the T-6600 profiler failed the precision criterion along the left wheelpath for three data sets, and along the right wheelpath for one data set, while the DNC 690 profiler failed the criterion along the right wheelpath for two data sets. On the rough PCC section, the DNC 690 and the T-6600 profilers failed the precision criterion for one data set along the left wheelpath and one data set along the right wheelpath

Southern Region

A review of the report showed that the average IRI and standard deviation of the IRI along each wheelpath for each data set were computed using all available runs for that data set. The average profiler IRI values obtained for the 80-km/h (50-mi/h) profiler runs and IRI obtained from the Dipstick measurements at the four sites that were extracted from the report are presented in table 50. The differences between the average profiler IRI and the Dipstick IRI for the profile runs obtained at 80 km/h (50 mi/h) are presented in table 51. Testing resulted in six data sets at each section; these tables only show the results obtained for 80 km/h (50 mi/h) testing, which comprise three data sets from a test section.

 

Table 50. Profiler IRI for 80-km/h (50-mi/h) runs and Dipstick IRI: Southern region.
Site Sequence Test Date Average IRI (m/km)
Left Wheelpath Right Wheelpath
T-6600 DNC 690 Dipstick T-6600 DNC 690 Dipstick
Smooth AC 1 11/06/96 0.72 0.73 0.70 0.74 0.73 0.75
2 11/08/96 0.71 0.74   0.74 0.73  
3 11/08/96 0.70 0.73 0.73 0.73
Rough AC 1 11/04/96 1.88 1.66 1.84 1.87 2.12 2.18
2 11/04/96 1.91 1.63   1.90 2.12  
3 11/04/96 1.96 1.61 1.92 2.12
Smooth PCC 1 10/30/96 1.76 1.79 1.67 1.78 1.69 1.77
2 10/31/96 1.74 1.77   1.76 1.69  
3 11/01/96 1.83 1.81 1.75 1.69
Rough PCC 1 10/30/96 2.05 2.15 2.28 2.48 2.09 2.35
2 10/31/96 2.02 2.16   2.50 2.09  
3 11/01/96 2.12 2.18 2.52 2.09
Note: Only one data set was obtained for Dipstick at each site.

1 m/km = 5.28 ft/mi

 

Table 51. Differences between the profiler IRI and the Dipstick IRI: Southern region
Site Sequence Test Date Average IRI (m/km)
Left Wheelpath Right Wheelpath
T-6600 DNC 690 T-6600 DNC 690
Smooth AC 1 11/06/96 -0.01 0.00 0.05 -0.01
2 11/08/96 -0.02 0.01 -0.08 -0.01
3 11/08/96 -0.03 0.00 -0.08 -0.02
Rough AC 1 11/04/96 -0.24 -0.45 -0.33 -0.31
2 11/04/96 -0.21 -0.49 -0.38 -0.28
3 11/04/96 -0.15 -0.51 -0.37 -0.26
Smooth PCC 1 10/30/96 0.07 0.10 -0.10 0.01
2 10/31/96 0.05 0.08 -0.07 0.01
3 11/01/96 0.14 0.11 -0.08 -0.02
Rough PCC 1 10/30/96 -0.04 0.06 -0.08 0.13
2 10/31/96 -0.07 0.07 0.02 0.15
3 11/01/96 0.03 0.10 0.04 0.17

1 m/km = 5.28 ft/mi

The findings from the main study are:

  • Both profilers passed the IRI bias criterion at the smooth AC site. At the rough AC site, both profilers failed the IRI bias criterion for all of the cases, except where the T-6600 profiler met the criterion along the left wheelpath for one data set. At the smooth PCC site, the DNC 690 profiler passed the bias criterion for all data sets, while the T-6600 profiler passed the bias criterion for all data sets along the right wheelpath, but failed the bias criterion along the left wheelpath for three data sets. At the rough PCC site, the DNC 690 profiler passed the bias criterion for all data sets, except for three data sets along the right wheelpath; the T-6600 profiler passed the bias criterion for all data sets, except for two data sets along the right wheelpath.
  • Both profilers passed the precision criterion at the smooth AC site. At the rough AC site, the DNC 690 profiler met the precision criterion for all data sets, while the T-6600 profiler failed the precision criterion along the left wheelpath for all data sets and along the right wheelpath for two data sets. At the smooth PCC site, the DNC 690 profiler met the precision criterion for all data sets; the T-6600 profiler passed the criterion for all data sets, except for three data sets along the left wheelpath. At the rough PCC site, both profilers met the precision criterion for all data sets, except along the left wheelpath where the T-6600 profiler failed the criterion for four data sets.
  • In most cases where the bias or the precision criteria were not met, testing was performed at 56 km/h (35 mi/h). The drivers appeared to have difficulty running the same wheelpath consistently at the slower test speed of 56 km/h (35 mi/h).

Western Region

For all profiler testing, each profiler was operated by the same driver. A review of the report indicated that nine profile runs usually were conducted for each data set. When computing the IRI bias for a particular wheelpath for a test speed, the average profiler IRI was computed by averaging the IRI values that were obtained for all profile runs for the three data sets and then subtracting the Dipstick IRI from this value. When computing the standard deviation of the IRI at a site for a particular wheelpath and a specific test speed, all profile runs obtained for the three test sequences were considered.

The average profiler IRI values obtained for the 80-km/h (50-mi/h) profiler runs and IRI obtained from the Dipstick measurements for the four sites that were extracted from the report are presented in table 52. The differences between the average profiler IRI obtained for the 80 km/h (50-mi/h) runs and the Dipstick IRI for each test sequence are presented in table 53. The values presented in table 53 were computed from the values shown in table 52. The report on this comparison did not give the values shown in table 53, since the differences between profiler IRI and Dipstick IRI were computed differently, as described previously.

 

Table 52. Profiler IRI for 80-km/h (50-mi/h) runs and Dipstick IRI: Western region.
Site Sequence Test Date Average IRI (m/km)
Left Wheelpath Right Wheelpath
T-6600 DNC 690 Dipstick T-6600 DNC 690 Dipstick
Smooth AC 1 10/10/1996 0.78 0.79 0.86 0.94 0.92 0.97
2 10/10/1996 0.78 1.15   0.93 0.91  
3 10/10/1996 0.75 0.80 0.91 0.93
Rough AC 1 10/15/1996 2.63 3.42 1.96 2.58 2.55 2.10
2 10/16/1996 2.53 3.50   2.52 2.63  
3 10/17/1996 2.60 3.13 2.67 2.56
Smooth PCC 1 10/11/1996 1.10 1.18 1.16 1.04 1.08 1.04
2 10/11/1996 0.97 0.95   0.87 0.90  
3 10/16/1996 1.83 1.81 1.75 1.69
Rough PCC 1 10/10/1996 2.24 2.33 1.99 2.46 2.41 2.12
2 10/11/1996 2.30 2.32   2.37 2.40  
3 10/16/1996 2.58 2.55 2.60 2.70
Note: Only one data set was obtained for Dipstick at each site.

1 On smooth PCC data collected with T-6600 on 10/10/96.

1 m/km = 5.28 ft/mi

The findings from the main study are:

  • Very high IRI bias values that were outside of the acceptable range were observed for both profilers at the rough AC and rough PCC sites. The report indicated that the high bias values were probably caused by the way Dipstick measurements were performed. The report also indicated that the documentation for the Dipstick measurement procedures being used at that time included the following paragraph: " The footpads should be placed to avoid minor localized cracks, holes, open joints, the edge of open joints or wide cracks, and loose stones or debris." The report indicated that this procedure was followed during Dipstick measurements. However, when profilers collect data, they do not avoid these features, so there were high bias values for the profilers at the rough AC and rough PCC sites.
  • High IRI precision values that did not meet the specified criterion were obtained in many cases.
  • After reviewing the report from this research project, the precision criterion failure at many of the sections is attributed to the procedure that was used for computing the precision. The other regions computed the precision for each data set. In the analysis performed by the Western region, all of the profiler runs obtained for all three sequences were used to compute the precision.

 

Table 53. Differences between the profiler IRI and the Dipstick IRI: Western region.
Site Sequence Test Date Average IRI (m/km)
Left Wheelpath Right Wheelpath
T-6600 DNC 690 T-6600 DNC 690
Smooth AC 1 10/10/96 -0.08 -0.07 0.04 -0.05
2 10/10/96 -0.08 0.29 -0.04 -0.06
3 10/10/96 -0.01 -0.06 -0.06 -0.04
Rough AC 1 10/15/96 0.66 1.46 0.48 0.45
2 10/16/96 0.56 1.54 0.42 0.53
3 10/17/96 0.63 1.16 0.57 0.46
Smooth PCC 1 10/11/96 -0.06 0.01 0.00 0.03
2 10/11/96 -0.18 -0.13 -0.16 0.11
3 11/16/96 -0.20 -0.21 -0.18 -0.14
Rough PCC 1 10/10/96 0.25 0.35 0.34 0.29
2 10/11/96 0.31 0.33 0.34 0.29
3 11/16/96 0.59 0.57 0.48 0.58

1 m/km = 5.28 ft/mi

Overall Comment on the Results

The procedures used by the four regions for computing the average IRI and the standard deviation of the IRI were different. The following procedures are used by each region in computing the average IRI and the standard deviation of the IRI:

  • North Atlantic Region: Five runs from each data set were used in the computations; however, these runs appeared to have been selected based on the review of the IRI values obtained from all of the replicate runs.
  • North Central Region: The first five error-free runs for each data set were used in the computations.
  • Southern Region: All available replicate runs for each data set were used in the computations.
  • Western Region: At each site, for a particular test speed, all runs that were collected at the site for all three test sequences were used in the computations.

Because of the different procedures used by the four regions in computing IRI bias and IRI precision, the results from the regions cannot be compared.

Overall, it appears that the T-6600 profilers are performing satisfactorily and, generally, data collected by the T-6600 profilers appear to be similar to the data collected by the DNC 690 profilers from an IRI viewpoint.

2002 VERIFICATION STUDY

In 2002, FHWA purchased four ICC profilers to replace the K.J. Law Engineers T-6600 profilers. Each RSC compared these two profilers before using the ICC profilers for data collection. A minimum of five test sites were used in each region for this comparison, and each region was asked to select at least one site meeting the following requirements: (1) smooth AC section with an IRI less than 1.6 m/km (101 inches/mi), (2) smooth PCC section with an IRI less than 1.6 m/km (101 inches/mi), (3) rough AC section with an IRI greater than 2.2 m/km (139 inches/mi), (4) rough PCC section with an IRI greater than 2.2 m/km (139 inches/mi), and (5) a chip-seal section. Dipstick measurements were not obtained at the test sites. The wheelpaths at the test sites were not marked, and the profiler operators judged the location of the wheelpath when profiling the test sections.

The purpose of this profiler comparison was to compare the IRI values and the profiles obtained by the two profilers. Each region collected data at the test sections following normal LTPP data collection procedures, except that the data collection at the PCC sections was performed in the afternoon. Each region was asked to submit IRI values for five error-free profile runs on each section for each profiler. At many of the sites, the two profilers collected measurements on the same day. However, at several sites, there was a time difference of up to 1.5 months between the measurements collected by the two profilers. Each region submitted the results of the comparison to the LTPP technical support services contractor, who prepared a report documenting the results obtained from all four regions.(28) Table 54 shows the IRI values that were obtained from the testing. This table shows the region, site number, surface type, dates when the sites were profiled, average left- and right-wheelpath IRI from each profiler, and the standard deviation of the IRI obtained from each profiler along the left and right wheelpaths.

The main findings of this study are:

  • Overall, the mean IRI values (average IRI for left- and right-wheelpath IRI) obtained by the two profilers showed good agreement. The difference in the mean IRI between the two profilers at the test sites was within ±0.05 m/km (±3.1 inches/mi) for the majority of the sites.
  • When individual wheelpath IRI values were compared between the two profilers, the differences were higher in magnitude than the differences observed when the mean IRI values were compared. When individual wheelpath IRI values at the test sites were compared, for 70 percent of the cases, the differences in the IRI were within ±0.10 m/km (±6 inches/mi). An evaluation of the results from the LTPP profiler comparison study that was conducted in 2000 in Texas indicated that the differences in the IRI that were observed between the K.J. Law Engineers and ICC profilers were comparable to the differences in the IRI that were observed among the four LTPP K.J. Law Engineers profilers.(14) This indicates that the IRI values obtained from the data collected with the ICC profilers show reasonable agreement with the IRI obtained from the data collected by the K.J. Law Engineers profilers.
  • The comparison of the profile plots indicated that there are differences in long wavelengths in the profile data recorded by the K.J. Law Engineers and ICC profilers at many of the sites. Visual reviews of the profiles showed that similar pavement features were being recorded by both profilers.
Table 54. IRI values obtained from the 2002 verification study.
Region Site Number Surface Type Profile Date Average IRI Left WheelPath(m/km) Average IRI Right WheelPath(m/km) Std.Dev IRI Left WheelPath(m/km) Std.Dev IRI Right WheelPath(m/km)
K.J. Law ICC Law ICC Law ICC Law ICC Law ICC
N.Atlantic 251002 AC 7/25/2002 7/25/2002 4.22 4.45 1.48 1.30 0.22 0.28 0.06 0.14
N.Atlantic 361011 AC 7/24/2002 7/24/2002 0.91 0.89 0.87 0.89 0.03 0.04 0.01 0.03
N.Atlantic 364018 PCC 7/25/2002 7/25/2002 2.64 2.87 2.22 2.18 0.09 0.16 0.06 0.05
N.Atlantic 245807 PCC 6/05/2002 8/01/2002 1.56 1.41 1.58 1.53 0.07 0.02 0.02 0.02
N.Atlantic 872811 AC 4/20/2001 7/31/2002 1.50 1.43 1.57 1.65 0.21 0.02 0.07 0.04
N.Atlantic 360801 AC 7/23/2002 7/23/2002 1.11 1.08 1.09 1.06 0.01 0.02 0.02 0.02
N.Atlantic 360802 AC 7/23/2002 7/23/2002 1.38 1.38 1.77 1.70 0.01 0.03 0.01 0.04
N.Atlantic 360859 AC 7/23/2002 7/23/2002 1.06 1.06 1.15 1.13 0.01 0.01 0.02 0.02
N.Central 17A001 AC 7/16/2002 7/16/2002 1.01 0.95 1.22 1.18 0.05 0.02 0.06 0.02
N.Central 17A002 AC 7/16/2002 7/16/2002 2.68 2.78 2.83 2.69 0.04 0.02 0.03 0.03
N.Central 17A003 PCC 7/17/2002 7/17/2002 1.06 1.08 1.15 1.16 0.02 0.02 0.01 0.02
N.Central 17A004 PCC 7/17/2002 7/17/2002 4.01 4.07 4.14 4.16 0.02 0.02 0.02 0.02
N.Central 17A005 CS 7/16/2002 7/16/2002 3.20 2.95 3.65 3.76 0.08 0.08 0.03 0.01
Southern 481064 AC 7/24/2002 9/10/2002 1.89 1.75 1.75 1.75 0.04 0.05 0.12 0.13
Southern 481070 AC 7/24/2002 9/10/2002 1.58 1.73 1.75 1.82 0.08 0.05 0.11 0.10
Southern 48B350 CS 7/24/2002 9/10/2002 1.84 2.32 1.75 2.45 0.16 0.13 0.10 0.25
Southern 483003 PCC 7/24/2002 9/11/2002 2.11 2.31 1.75 2.26 0.02 0.06 0.07 0.04
Southern 485253 PCC 7/24/2002 9/11/2002 1.29 1.67 1.75 1.56 0.01 0.02 0.02 0.02
Western 320110 AC 6/10/2002 7/31/2002 0.57 0.57 0.74 0.74 0.01 0.01 0.01 0.01
Western 320209 PCC 6/10/2002 7/31/2002 1.03 1.21 0.96 1.11 0.03 0.03 0.02 0.03
Western 67454 AC 7/26/2002 7/26/2002 2.24 2.27 2.32 2.19 0.02 0.03 0.04 0.06
Western 69107 PCC 7/25/2002 7/25/2002 2.58 2.50 2.29 2.38 0.03 0.07 0.03 0.08
Western 169034 CS 6/04/2002 7/29/2002 1.81 1.74 2.02 1.98 0.03 0.05 0.08 0.09

1 m/km = 5.28 ft/mi

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The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT).
The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT). Provide leadership and technology for the delivery of long life pavements that meet our customers needs and are safe, cost effective, and can be effectively maintained. Federal Highway Administration's (FHWA) R&T Web site portal, which provides access to or information about the Agency’s R&T program, projects, partnerships, publications, and results.
FHWA
United States Department of Transportation - Federal Highway Administration