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The cell phone records were merged with the trip summary data set to generate a data set of all files where:

 The call began after the start of the file, and ended before the end of the file.

 The call began after the start of the file, and ended after the end of the file.

 The call began before the start of the file, and ended before the end of the file. A total of 14,754 calls and 8,610 text messages were exchanged while the vehicles were in operation (i.e., the ignition was turned on).

To identify how drivers were specifically using their cell phones while driving, 10 percent of the calls, with a minimum of four calls per driver, were randomly sampled. Likewise, 10 percent of the text messages, with a minimum of four text messages per driver, were randomly sampled. Since start time and duration of calls were rounded to the nearest minute, calls in the log that occurred at the same time were omitted from computations of the amount of time drivers

conversed on the phone while operating their vehicle. Duplicate calls were not omitted from any frequency computations, however. The same approach was used for text messages. A total of 1,564 calls and 844 text messages that occurred when the vehicles were in operation were sampled. This comprised a total of 2,408 cell phone use samples.

Because the large majority of cell phone records were rounded up (one cell phone provider rounded down) to the nearest minute, the exact start and end time of each sampled call and text had to be identified by viewing the video data. Furthermore, since the records only listed the time and direction of the calls, the type of cell phone used to make the call also had to be visually determined (via video review). Each sample was reviewed in a customized data reduction software application by a team of data reductionists. Samples were omitted if: (1) the video was not available, (2) the wrong driver was present, (3) a passenger was the individual using the cell phone, (4) the video footage ended just before the cell phone interaction began, or (5) the video footage began just after the cell phone interaction ended. A total of 2,108 cell phone samples remained. Reductionists then recorded the exact start and end frame for every cell phone subtask pertaining to the sampled interaction. The following cell phone subtasks were recorded (Table 7). Operational definitions for each subtask are presented in Appendix A3.

Table 7. Subtasks Reduced

Subtask Abbreviation

Hand-Held: Locate/Reach/Answer HH: Locate/Answer

Hand-Held: Dialing HH: Dial

Hand-Held: Talk/Listen/Voice Commands HH: Talk/Listen

Hand-Held: Text Messaging HH: Text

Hand-Held: Viewing/Browsing/Reading HH: Browse/Read

Hand-Held: End Task HH: End Task

Hand-Held: Holding HH: Hold

Portable Hands-Free: Locate/Put-on Headset/Earpiece PHF: Locate/Put on Portable Hands-Free: Push Button to Begin/Answer PHF: Begin/Answer Portable Hands-Free: Talk/Listen/Voice Commands PHF: Talk/Listen Portable Hands-Free: Push Button to End PHF: End Task Portable Hands-Free: Holding/Wearing Headset/Earpiece PHF: Hold/Wear Integrated Hands-Free: Press Button to Begin/Answer IHF: Begin/Answer Integrated Hands-Free: Talk/Listen/Voice Commands IHF: Talk/Listen Integrated Hands-Free: Press Button to End IHF: End Task

Cell Phone Navigation Navigation

Other Cell Phone Task Other

To clarify terminology used in this report, a cell phone subtask refers to a specific action the driver takes when using a cell phone (such as dialing), while a cell phone interaction refers to the series of subtasks that took place during the sampled call or text. The start and end points of the subtasks bounded the data reduction performed on them. However, because talking on a cell phone could be a lengthy subtask, only a random 6-second interval of the talking subtask was selected for further reduction. Care was taken to ensure that talking was the only cell phone subtask that took place in the sample. Furthermore, any holding of the cell phone or wearing of a PHF headset/earpiece that lasted longer than 5 s was treated as a separate subtask. Similarly to talking on a cell phone, a random 6-second interval was sampled since this subtask could also be quite long in duration. If the holding subtask lasted longer than 30 s, then the search for the beginning or end of the subtask was halted.

button on his Bluetooth earpiece to begin a PHF cell phone call, (2) talking using the PHF earpiece, (3) browsing the HH cell phone during the PHF conversation, (4) putting the HH cell phone down and continuing to talk for another minute, (5) browsing the HH cell phone again during the conversation, (6) putting the HH phone down again and continuing to talk for another minute, and (7) pushing a button on the earpiece to end the call, then only the first browsing while talking subtask combination would be selected for reduction. For each sampled subtask, reductionists answered 49 questions pertaining to the driver, vehicle, and environmental factors present. These parameters are listed in Appendix A4. Reductionists also recorded the drivers’ eye glance locations over the span of each subtask. Eye glance locations were recorded at 10 Hz (Appendix A5).

Kinematic data recorded at the time of each subtask were queried from the data set. The list of variables that were considered is presented in Appendix A6.