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Several agencies also mentioned quality and timeliness of Question: How long is the contracting
the data as important factors. However, whereas some agencies period?
gave this reason in support of outsourcing the data collection,
others used it to justify their decisions to continue collecting 1 year
data with in-house resources. This disagreement appears to 11.5%
indicate that there are different degrees of satisfaction with > 3 years
the quality of the contracted services. 30.8%
2 years
34.6%
Service Provider Selection
3 years
23.1%
The outsourcing of the data collection services typically begins
with the issue by the owner agency of a request for proposals
(RFP) or terms of reference document. This document outlines FIGURE 7 Length of the contract
the services that are being requested, minimum quality require- period for outsourced pavement
ments for these services, required service provider qualifica- data collection services.
tions, and selection criteria. The main criteria used for service
provider selection include past performance/technical ability
(39%), best value (31%), and low bid (12%).
reviewed for the preparation of the synthesis appears to indi-
The process often requires a pre-qualification of the poten- cate that more agencies request that the service providers
tial service providers before the economical offers are con- collect multiple pieces of information. For example, the latest
sidered. For example, some states require service providers Louisiana Department of Transportation and Development
to evaluate some control section and meet specific accuracy (LADOTD) RFP (21) included the following services: pre-
requirements. The New Mexico DOT has taken a unique liminary activities (including training of raters and work-
approach; the agency has contracted the distress data collection station delivery); collection of global positioning system
through a professional service agreement with a group of (GPS)-referenced, clear digital pavement (grayscale) and
universities within the state. right-of-way (color) images and profile data for each district;
distress quantification for all roads tested; and final docu-
mentation of the project.
Contract Characteristics
The LADOTD service provider selection criteria included
The contracts are typically let based on a cost per mile (58%), the following factors: firm experience on similar projects
with some having a lump-sum fixed price (31%) and a few (16% of the weight), personnel experience as related to the
agencies citing other contracting modes. One agency reported project (16%), the consultant's understanding of the project
using a cost per kilometer for network-level evaluations, and a
requirements as evidenced in the proposed work plan (16%),
fee for service for project-level surveys. Although no agency
field trials (16%), and price (36%). The RFP requires that
reported using performance-based contracts, McGhee (6)
the consultant deliver on a weekly basis the following data:
found that in 2003 most data collection service contracts
collected right-of-way images, raw data from the consultant's
included a quality assurance provision, approximately half had
Data Collection Vehicle's electronic sensors (rutting, IRI,
price adjustment clauses, and a smaller fraction of the con-
faulting, and GPS data), equipment calibrations test results
tracts included warranty provisions.
(i.e., distress manifestation index, rut measurement device,
video foot print, etc.), and electronic sensor verification results.
The survey conducted for this synthesis revealed that sev-
eral of the data collection contracts (39%) included clauses that The acceptance plan called for LADOTD personnel to eval-
link payment to the quality of the data collected; 32% of the uate the pavement images and condition data summary to
contracts do not include such clauses and 29% of the respon- look for discrepancies and the right-of-way images for quality
dents were not sure about the terms in the contract. The length assurance. Other examples are presented in the case studies
of the contracting period is highly variable (see Figure 7), rang- reviewed in chapter five.
ing from one year to more than three years. Longer contracting
periods might lead to more consistency in the data, because ISSUES ASSOCIATED WITH
the possible change in service providers during the successive LOCATION REFERENCING
bidding may introduce another source of variability.
Location referencing is an important part of pavement man-
Although McGhee (6) found in 2003 that agencies were agement because it allows agencies to manage data spatially
contracting only a particular data collection activity (e.g., and with respect to time. This is important because meaning-
network-level smoothness measurement), the information ful analysis generally requires multi-year condition data of
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14
the same pavement segments to determine pavement deteri- Linear Referencing
oration trends and provide optimum preservation strategies.
In addition, accurate referencing also allows overlaying con- The prevalent location referencing used in highway applica-
dition indicators and other relevant parameters to identify tions is linear referencing. Linear referencing methods consist
sections in need of work, select appropriate interventions for of procedures for specifying a location as a distance, or offset,
those sections, and design the specific treatments. Therefore, along a linear feature (highway network), from a point with
the quality of the location referencing data is paramount for known location (25). Common linear location referencing
efficient pavement management. Quality management prac- methods include route/milepost, link-node, reference point/
tices include checks for the location data. Location referencing offset (using a distance measurement instrument or distress
problems may affect the pavement condition data quality and manifestation index), and street address.
the decisions supported by these data. For example, poor loca-
tion data may make it difficult to overlap different pavement
Spatial Referencing
indicators (e.g., roughness and cracking), develop time-series
for performance prediction, link condition with traffic, etc. The use of spatial location referencing based on GPS is becom-
ing more prevalent as the technology becomes more afford-
A location referencing method refers to a technique used able and accurate. The use of GPS to mark the location of
in the field or in the office to identify the specific location of distressed areas prevents some of the errors encountered by
an asset. Commonly used location referencing methods can be using milepost methods. Because the location is known in
grouped in linear and geodetic (or spatial) reference methods. terms of coordinates, the relocation of a milepost or road
A location referencing system constitutes a set of procedures realignment will not affect the true location of the distressed
for determining and retaining a record of specific points in a area. This mitigates the problem of losing historical data when
transportation network. This system includes one or more
a new segmenting system is implemented and aids with inter-
location referencing method, as well as procedures for stor-
agency data sharing because coordinates can be converted for
ing, maintaining, and retrieving information about points and
use in other referencing schemes. The use of GPS also provides
segments on the network (22). State-of-the-art referencing
for easier data integration, allowing for the possibility of a more
systems can handle more than one referencing method and
comprehensive and universal location referencing system. The
datum (22, 23).
use of spatial/geodetic location referencing facilitates inter-
agency standardization (26).
Effective location referencing systems are comprehensive
and can be used within and among agencies. This means that
objects in the referencing system must be represented as they Current Practice
are in the real world. For example, roads and highway segments
can be represented as one- or two-dimensional objects; that is, Figure 8 presents the location referencing methods used to
lines or polygons, and interchanges may be represented in three support the pavement data collection activities by the agencies
dimensions. Additionally, because an object's characteristics that responded to the survey. It is noted that some agencies
may change with time, it is necessary to include a standard use more than one method. Most agencies (86%) use mileposts
temporal reference, such as a date of inspection (24). and milepoints. This is a classic example of a linear reference
Question: What type of location referencing is used to support the pavement
data collection activities?
100%
90% 85.7%
80%
Percentage of Agencies
70%
60%
50% 46.4%
40%
30% 26.8%
20% 14.3%
10% 7.1%
0%
Milepoints and Link-Node Global National Other
Mileposts Positioning Differential GPS
System (GPS) (NDGPS)
FIGURE 8 Types of location referencing used.
