Roadway Geometry and Inventory Trade Study for IntelliDriveSM Applications Applications
CHAPTER 6. RECOMMENDATIONS AND OPTIONS TO ADDRESS DATA GAPS
This chapter summarizes options and recommendations for developing and maintaining the roadway geometry and inventory databases needed to support future IntelliDrive applications. The first subsection deals with refining and standardizing the roadway data requirements. The second discusses options for building a roadway geometry database. The third discusses regulatory options to support the initiative, and the final subsection lists research needs.
REFINE AND STANDARDIZE INTELLIDRIVE ROADWAY DATA REQUIREMENTS
An issue encountered throughout this study is the inconsistency in roadway feature and attribute definitions, attribute domain values, positional and attribute measurement accuracies, and update frequencies for many of the identified roadway attributes across roadway data collection organizations. This issue underscores the need for development of data standards for roadway geometry and inventory data to support IntelliDrive applications. The standards development process needs to be collaborative, with participation from key stakeholder groups, including, at a minimum, IntelliDrive application developers; Federal, State, and local transportation agencies that collect roadway data; and commercial roadway database developers.
Key issues that should to be addressed through standards development include the following:
- What roadway geometry and inventory data should be provided using a geospatial roadway database versus other data delivery methods such as signal phase and timing data transmitted to a vehicle as it approaches an intersection or vehicle on-board sensor measurements?
- Which roadway features and attributes are essential for specific IntelliDrive applications and which are desirable? Which features and attributes are required for all road segments versus specific types of environments (e.g., complex intersections)?
- What level of feature resolution is needed? (e.g., How should lane-specific attributes, such as lane width or use restrictions, be represented in a roadway database?)
- How can feature and attribute definitions be unambiguously defined? (e.g., What does vertical curvature or available sight distance mean? Where does a bridge begin and end?).
- What are the units of measurement and required accuracy for attributes (e.g., lane and pavement width, curve length and radius, or cross slope)?
- What is the acceptable maximum absolute positional error for specific roadway features? Can this accuracy be collected using current data collection methods?
- How frequently are updates needed? Which attributes must be kept current to ensure safety? How quickly must updates be incorporated into the on-board roadway database?
- Are the standards that emerge from this process mandatory or voluntary? (i.e., Should standards for data definitions, measurement, and positional accuracies be incorporated into Federal reporting requirements?)
The standards development process for IntelliDrive roadway data will be highly technical in nature, time-consuming, and iterative. It will require significant commitments of time and energy from specific stakeholder representatives. Early phases of the process will involve education and information sharing on such topics as geospatial data structures, roadway data collection methods, and IntelliDrive applications and processes. Later phases will involve preparation of standards specification documents and convincing other members of the stakeholder communities that the standards are both necessary and beneficial.
The U.S. DOT can play several roles in the development of standards, including active participation as a Federal stakeholder, the sponsor and facilitator of meetings and workshops related to standards development, and ultimately, a champion for standards that emerge from the development process.
OPTIONS FOR BUILDING A ROADWAY GEOMETRY AND INVENTORY DATABASE
While the development and promulgation of data standards are important steps in building a roadway geometry and inventory database for IntelliDrive applications, the ultimate goal is to create a geospatial data product containing the roadway geometry and inventory data items that are needed to support nationwide deployment of specific IntelliDrive applications. Additionally, once the initial database is developed, organizational structures and procedures must be in place to keep the data current and to disseminate updated information efficiently to IntelliDrive-equipped vehicles throughout the United States.
There are several possible options for building and maintaining an IntelliDrive Roadway Geometry and Inventory Database. These options are discussed along with each option's potential strengths and weaknesses.
Option 1
The first option is a public sector development initiative using public domain data and managed by a Federal agency with authority (and adequate resources) to build and maintain the database.
Under this option, a public sector agency (presumably the U.S. DOT or one of its operating agencies) would develop a national geospatial roadway network database containing many or all of the data items needed to support IntelliDrive applications and make it available as a public domain data product similar to the Census Bureau's TIGER/Line® database.
Developing a public domain roadway database would be extremely costly and time-consuming.1 However, it also would provide the U.S. DOT with the greatest amount of control over data content, accuracy, and accessibility by all stakeholders and would enable the U.S. DOT or other stakeholders to add new data content without concerns about proprietary restrictions on derivative products.
Development of a national geospatial roadway basemap would need to begin from an existing public domain database. This could be either the most recent Census TIGER/Line® road network or possibly a nationwide all-road geospatial database purchased from a commercial roadway developer. The Bureau of Transportation Statistics (BTS) negotiated a similar purchase nearly 10 years ago with Geographic Data Technologies to acquire a slightly out-of-date (18 month old) roadway network database with limited attribute information and place it in the public domain. The primary benefit of using a public domain version of a commercial network over the Census TIGER/Line® network is that the commercial network would require relatively little additional processing to achieve network connectivity.
Once the base roadway network is acquired, roadway attribute data would have to be collected or compiled from public sources such as State DOTs, local roadway agencies, other Federal agencies, etc. Each new roadway attribute would require resources either for primary data collection or for compiling, verifying, and reconciling attribute data. Development and population of a public sector roadway network database would provide a platform for integrating and enhancing roadway data contained in national inventories such as HPMS, NBI, and HRCI and may facilitate the establishment of a national geospatial data repository for transportation data.
Option 2
The second option is a public sector roadway database that is maintained by a private sector contractor under the sponsorship (and funding) of a public agency.
One of the limitations of the public sector model is that State and national geospatial roadway networks and roadway inventory databases are not maintained or updated in a timely manner. The national inventory databases such as HPMS receive updates from State DOTs on an annual basis, but some of the data elements are based on periodic inspections or data collection that take place on 2-, 3-, or 4 year cycles. One way to overcome this would be through a long-term contract with a commercial database firm to update and maintain the roadway database, with the U.S. DOT sponsoring (and funding) the effort.
An important yet currently unanswerable question is whether any commercial roadway database developer would be willing to accept a contract to maintain and update a public domain roadway database that potentially competes against its own proprietary product. If so, how would the developer differentiate its own product from the public domain product, and would these differences still enable the public domain database to meet IntelliDrive application needs? Finally, how costly would such a maintenance agreement be?
Option 3
The final option is a private sector model where current (and possibly new) roadway database developers compete to market commercial databases to IntelliDrive application developers.
Given the current status of roadway data collection in the United States, a third option is the development of a roadway geometry and inventory database built upon commercial roadway databases. In general, work flow processes such as data collection, storage, updating, quality control, and dissemination are more clearly defined and better integrated among commercial roadway database developers than among public agency sources. In this private sector model, current (and possibly new) roadway database developers would compete to market their own commercial databases to IntelliDrive application developers.
The results of the trade study indicate that commercial developers such as NAVTEQ™ and Tele Atlas® would be strong candidates for this option. Both the NAVTEQ™ and Tele Atlas® databases currently provide basic nationwide geometry for all roads with enhanced positional accuracy and attribute data on higher functional class roads intended specifically for use in IntelliDrive applications. Furthermore, both firms have conducted internal research and development efforts to explore data collection and updating and transmission methods, as well internal and external data communication and processing protocols, and both seem to understand and appreciate the challenges of creating data that need to interface with computers rather than people. Additionally, NAVTEQ™ and Tele Atlas® have the necessary field staff in place to collect and update their roadway data in a timely and efficient manner. Finally, NAVTEQ™ and Tele Atlas® both reported current business plans in place to support IntelliDrive application needs.
INSTITUTIONAL AND REGULATORY OPTIONS
This trade study revealed that State and local roadway management agencies are very reluctant to increase their data collection activities without financial incentives or regulatory mandates. It is recommended that the U.S. DOT implement one or more of the following institutional and regulatory options to encourage new data collection activities among State and local roadway management agencies to better support IntelliDrive data needs.
Option 1
One option is to monitor and participate in ongoing national roadway data sharing initiatives.
A major national data-sharing initiative known as Transportation for the Nation (TFTN) is currently underway. Its purpose is to create a public domain national geospatial roadway layer from the "best available" data collected by all levels of government. The effort is being supported by the National States Geographic Information Council, the U.S. Geological Survey (USGS), the Census Bureau, and the U.S. DOT. The initiative follows the same approach as the previously successful Imagery for the Nation. At a minimum, this effort should be monitored by IntelliDrive to determine what data items, if any, might be included in TFTN that could be used for IntelliDrive applications. Through active participation, IntelliDrive representatives might be able to add new data items from the IntelliDrive roadway data list or be able to identify additional local data sources for specific attributes.
Additionally, TFTN could prove to be a strong ally for both the development and promulgation of roadway data standards and the development of a public sector roadway database.
Option 2
Another option is to consider the availability of local roadway data as a selection criterion for future IntelliDrive demonstration grants.
It is likely that early IntelliDrive deployments will involve operational demonstrations in specific geographic areas and that Federal funding grants will be awarded to local jurisdictions to help support equipment purchases, project oversight, and demonstration evaluation activities. In awarding future IntelliDrive demonstration grants, the U.S. DOT should include the availability and quality of local roadway data as either a prerequisite or an important criterion for selection. This provides an incentive for State and/or local agencies to collect roadway data to support IntelliDrive deployment but does so without regulatory mandate.
RESEARCH INITIATIVES
The study identified several roadway geometry or inventory data items that were not being collected extensively enough to be useful for nationwide IntelliDrive applications. This suggests that one or more research efforts may need to be undertaken to investigate the feasibility and practicality of collecting specific data items using existing or emerging technologies and new methods for data integration and standardization across multiple data sources. The following federally sponsored research projects are recommended to help move forward the development of a roadway database to support IntelliDrive applications.
Project 1
Investigate and test the accuracy of IFSAR technology to develop a 3 D roadway centerline network.
The use of IFSAR technology to develop a 3 D nationwide roadway centerline database could potentially produce an accurate and consistent database of horizontal and vertical roadway curvature, grade, and elevation for all U.S. roads, including local roads. The cost to process the already collected IFSAR imagery is likely to be substantially less than any other current data collection method. However, before any decision is made to proceed with this technology, the following research should be undertaken: (1) verify the horizontal and vertical accuracy levels claimed by the technology developer, (2) evaluate if these accuracy levels meet IntelliDrive application requirements, and (3) examine the costs and use limitations to acquire the 3 D roadway centerline database and place it in the public domain.
Project 2
Examine the feasibility and costs of using mobile LIDAR to collect selected roadway geometry and inventory data.
Some roadway geometry data, including roadway cross slope, lane, shoulder, and clear zone width cannot be collected using IFSAR technology and cannot be measured accurately from videologs. Research should be undertaken to examine the costs and feasibility of collecting and processing multiple roadway data items using mobile LIDAR, either by itself or in combination with videolog feature extraction. The study could explore use of the technology in several roadway environments (e.g., urban, rural high-volume freeway, rural low-volume road, mountainous verses flat terrain) in order to develop a cost profile for collecting key roadway data items on a per-mile basis.
Project 3
Coordinate IntelliDrive roadway data research with safety research activities currently underway through SHRP2.
SHRP2 is currently sponsoring a naturalistic driver behavior study, which will explore the relationships between driver behavior and roadway environment in contributing to vehicle crashes. The study is being conducted at six study area locations and will include the collection of detailed roadway inventory data similar to that identified by IntelliDrive stakeholders at each of the six sites. The data collection activities undertaken at these sites should provide considerable insight into the availability of specific roadway data items, the costs of collecting new data, and the relevance of the data for vehicle crash avoidance. The IntelliDrive program should coordinate closely with this research effort, sharing information on data collection technologies, roadway database standards, and even support for specific data collection activities (e.g., processing of IFSAR imagery).
Project 4
Work with State DOTs to demonstrate the potential benefits of collecting specific additional roadway data items in their business process.
The trade study revealed that few State DOTs have successfully implemented agency-wide standards for data collection such as database documentation, quality control/quality assurance criteria, update or reverification frequency, or even storage media. The IntelliDrive Program could sponsor projects with specific State DOTs to demonstrate the benefits and costs to implementing agency-wide standards for roadway data collection.
Project 5
Expand research done through NCHRP 08-70—Target-Setting Methods and Data Management to Support Performance-Based Resource Allocation by Transportation Agencies to develop a data governance model for IntelliDrive.
NCHRP 08-70 is developing recommended data management and governance techniques for the application of performance measures in State DOTs. It also is identifying the ways data management systems and organizational units within a State DOT can be used to ensure the use of accurate, timely, high-quality data for decisionmaking purposes. Many of the concepts such as data stewardship and data governance maturity models would be relevant to the development of a data management process to support IntelliDrive.
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