----Choose A Traffic Image---- I-95 N&S Nov. '01 I-95 N Nov. '01 I-95 S Nov. '01 I-95 N&S Full Year '01 I-95 N Full Year '01 I-95 S Full Year '01 Maine Mall Rd. Full Year '01 I-95 S Type 11 I-95 N Type 11 Bethel E Overweight Type 10 Bethel W Overweight Type 10 Bethel E Percent Overweight Type 10 Truck Speed Percent Truck Speed

Kittery, Maine   Interstate 95 North and South     November 2001

The JOHO image above is an example of the use of American Image Inc.'s innovative visualization technique. Using JOHO, you can make displays from your large traffic information bases. You can quickly discern patterns and exceptions to the patterns, even in the large data sets produced with vehicle sensors.

The discussion below will help you to understand how JOHO constructs images. It serves as a good introduction before looking at the other JOHO images on this site.

This image shows the total number of vehicles on Interstate 95 in Kittery, Maine (the southernmost tip of the state) for every hour in November 2001. The image contains 720 data points. This is more information than traditional graphics programs can display.

The traditional way to look at this kind of information would be to use line graphs or bar charts. To look at one month's hourly data, you might make one graph with thirty superimposed lines on it, each in a different color or using a different symbol. Alternatively, you might make thirty separate bar charts, each covering one day.

These graphs and charts take a long time to produce, and are difficult or impossible to interpret.

To make a JOHO image of the same data, we use data from one day to make one row in a grid. In the traditional graph, the height of the line above the axis represents the value of the measurement (number of vehicles). In the JOHO image, this value is represented by a color. This makes it possible for JOHO to quickly put many more measurements on the screen, and makes it possible for us to easily recognize trends, exceptions, and other patterns in the information.

Image Layout

The image has one panel showing November 2001. As labeled on the left side of the panel, the 24 cells in the top row represent the hours in the first day of November. The bottom row of cells represents the last day of November. We have also indicated the day of the week on the right side of the panel. The time through each day is measured horizontally along each row, from the hour beginning at midnight on the left to the hour beginning at 11 PM on the right. Noon is halfway across the panel.

Each colored cell indicates the total number of vehicles passing the sensor at that day during that hour. The legend at the right indicates the relation between color and number of vehicles. The image indicates counts of fewer than 3,000 as the dark blue color at the bottom of the legend. At about 5,500 vehicles the color changes from green to orange. The white at the top of the legend indicates a count of 11,000 vehicles or higher. (Traffic never got that heavy in November.)

Image Interpretation

Traffic volume at this site is predominately affected by people coming to Maine for the weekend. The first three weekends show the typical weekend pattern with high traffic on Friday evening and a broader traffic peak during the afternoon on Sundays. Thanksgiving weekend is very different. There is heavy traffic late on Wednesday afternoon. The traffic on Thanksgiving Day drops off very suddenly at about noon.  On Sunday the traffic picks up again as visitors return to their weekday homes.

The late start of traffic on Saturday November 3 and Sunday November 4, and the peak at 8 AM on Monday November 5 are unusual.

More Traffic Information

This image shows the traffic counts for only one month. Longer trends and seasonal effects appear in the JOHO image that covers the entire year. While 720 data points is difficult for traditional graphics programs, visualizing an entire year of hourly data (8,760 data points) is simply impossible without averaging or otherwise destroying information. JOHO makes even this amount of information easy to display and interpret.

The directional dependence of the traffic is visible in the November northbound and southbound images. The full year northbound and southbound images clearly show the component that is due to commuter traffic heading south in the morning and north in the afternoon, with a volume that is consistent throughout the year.

This site also contains FHWA Type 11 images and overweight FHWA Type 10 images that show how the Maine DOT is using JOHO to monitor their sensors and to understand traffic patterns throughout the state.