# Big Data for Traffic Estimation and Prediction: A Survey of Data and Tools
## 2 Data-Driven Traffic Estimation and Prediction
### Trip Surveys  
Trip surveys are detailed questionnaires on mobility habits, which are usually collected by local authorities or researchers. Sometimes, this is only a way to accurately measure and understand people's changing daily travel patterns, when different travel modes are considered and location privacy is not violated. For example, in the \"My Daily Travel Survey\" ([[https://www.cmap.illinois.gov/data/transportation/travel-survey#My_Daily_Travel_Survey](https://www.cmap.illinois.gov/data/transportation/travel-survey#My_Daily_Travel_Survey)]([https://www.cmap.illinois.gov/data/transportation/travel-survey#My_Daily_Travel_Survey](https://www.cmap.illinois.gov/data/transportation/travel-survey#My_Daily_Travel_Survey))) by the Chicago Metropolitan Agency for Planning between August 2018 and April 2019, households in northeastern Illinois were asked to record the trips they made for work, school, shopping, errands, and socializing with family and friends.  
Another example is the \"California Household Travel Survey (CHTS)\" ([[https://www.nrel.gov/transportation/secure-transportation-data/tsdc-california-travel-survey.html](https://www.nrel.gov/transportation/secure-transportation-data/tsdc-california-travel-survey.html)]([https://www.nrel.gov/transportation/secure-transportation-data/tsdc-california-travel-survey.html](https://www.nrel.gov/transportation/secure-transportation-data/tsdc-california-travel-survey.html))) by the National Renewable Energy Laboratory (NREL) between 2010 and 2012. As the largest such regional or statewise survey ever conducted in the United States, detailed travel behavior information was obtained from more than 42,500 households via multiple data-collection methods, including computer-assisted telephone interviewing, online and mail surveys, wearable (7574 participants) and in-vehicle (2910 vehicles) global positioning system (GPS) devices, and on-board diagnostic sensors that gathered data directly from a vehicle's engine.  
Details of personal travel behavior were gathered within the region of residence, inter-regionally within the state, and in adjoining states and Mexico. The survey sampling plan was designed to ensure an accurate representation of the entire population of the state.  
Among the participating households, 42,436 completed the travel diary survey portion, 3871 completed the wearable GPS portion, and 1866 completed the vehicle GPS portion of the study. Trip details, including purpose, mode, travelers, tolls, departure time, arrival time, and distance were collected for both private vehicles and public transit trips. More trip surveys are available on the internet ([[https://www.nrel.gov/transportation/secure-transportation-data/tsdc-cleansed-data.html](https://www.nrel.gov/transportation/secure-transportation-data/tsdc-cleansed-data.html)]([https://www.nrel.gov/transportation/secure-transportation-data/tsdc-cleansed-data.html](https://www.nrel.gov/transportation/secure-transportation-data/tsdc-cleansed-data.html))).  
The pros of trip surveys include high-resolution and detailed information, which contain trip information directly and eliminates the need for traffic estimation. The cons of trip surveys include small sample size, limited spatial and temporal scale, self-reporting errors, and high cost to collect, which limits the availability of such data as well as real-time applications, e.g., they are less used for traffic prediction.