Most current transportation systems are at or have exceeded their maximum capacity, and adding capacity through building is no longer a viable option due to space or environmental constraints. Better planning - at the city, regional, and state levels - can reduce the demand on the transportation system.
This requires a better understanding of traveler behavior, but gathering complete information via surveys has been problematic. To accurately capture the full spectrum of travel behavior, longitudinal surveys using GPS have shown great potential. GPS-based surveys are more accurate and minimize the respondent burden. In addition, GPS digital data can be readily imported into computer analysis programs.
The GPS-aided electronic travel diary has the strongest potential to fully and accurately capture all travel behavior for accurate modeling. The drawbacks of previous GPS-aided travel diaries and loggers can be overcome by tight component integration, additional sensors, longer-lasting backup batteries, and increased on-board processing power and intelligence. A system is needed that can record traveler location, time, speed, and trip information. Surveys can then be carried on for a long duration while maintaining survey data accuracy and minimizing burden on the respondents. The GPS-ATD was developed to address these needs.
We designed the prototype GPS-ATD to be mass-produced and deployable for future full-scale household survey. The surveys will provide decision makers with current, accurate, and reliable traveler behavior data.
System requirements
Automation is the key to reducing respondent burden and increasing accuracy and data integrity. To lower the cost, weight, complexity, and power consumption of a GPS-aided electronic travel diary, its required CPU tasks should be minimized. Therefore, longitudinal travel surveys should be divided into two phases: data collection and data post-processing. The GPS-aided diary should be designed only to collect all necessary raw data for the subsequent data post-processing and analysis phase. Researchers and analysts may then process and re-process the raw data with various criteria and methods in conjunction with the latest GIS information updates in the post-processing phase.
Based on previous research, we recommended that the GPS-ATD should support survey duration of approximately four weeks without data download. This allows capturing the various patterns of the average traveler. Intra-week surveys tend to only capture quick and short-term travel patterns, and fail to fully sample long-term long-trip travel patterns.
In general there will be two diary units: one for the vehicle, and one portable unit for each user. These two units will share common features and functionality. Both vehicular and wearable personal versions will be based on a shared modular system architecture. Moreover, they must be simple to use, robust, compact, low-power, light weight, simple to install, esthetically pleasing, rugged, and low-cost for easy implementation in a wide array of vehicles, or travel modes for the portable units. The sensor outputs - positional and temporal data - will be collected automatically by an on-board embedded processor and stored in solid-state memory. The overall system will be easily installable by the end-user.
The human-machine interfaces should address biases of potential language barriers, literacy, or technology illiteracy. The user interface will be based on a sunlight readable LCD and application-specific buttons. This interface should be intuitive, fast, and result in reduced user burden.
The wearable personal GPS-ATD will capture all modes of transportation.