"Spatial" functionality
Spatial Query - Box Select
Engineering Task - Downtown Crashes
To begin, first proceed through the process to identify your region
of interest. That is, begin by selecting ALAS File from the menubar,
then select View Map from this menu. Proceed through the questions,
selecting the region type (County), the region desired (Story), the
timeframe of interest (1993-1997), and whether you want to use actual
crash locations or nodes for your selection (choose actual crash locations).
Once this has been completed, you should have a map showing Story County
roads, rails, rivers, and 1993-1997 crashes, shown in Figure 1.
Using the zoom-in tool, zoom to the Ames area (the large city on the
western edge of the map). First, move the mouse pointer to the zoom-in
tool button (
)
and click with the mouse to select it. Then proceed by placing the zoom
button at one corner of a box that would contain Ames, pressing and
holding down the left mouse button, dragging the mouse to the opposite
corner of the box, and releasing the button. The box to be drawn (though
difficult to see) is shown in Figure 2.
The resultant map should look somewhat like the one shown in Figure
3.
Next, using the box selection tool, select the Ames downtown region,
as shown in Figure 4. First, move the mouse pointer to the box select
tool button (
)
and click with the mouse to select it. Then proceed by placing the zoom
button at one corner of a box that would contain downtown Ames, pressing
and holding down the left mouse button, dragging the mouse to the opposite
corner of the box, and releasing the button. The box to be drawn (though
difficult to see, is shown in Figure 4.
The resultant map should look somewhat like the one shown in Figure
5.
From here, select Request from the menubar, then select Crash
Locations from this menu. A box giving the number of crashes for
the selected region will then appear. An example of the answer is shown
in Figure 6. Note: You should only arrive at the same answer if you
selected the EXACT same region as is selected here.
Another dialog box, shown in Figure 7, will appear, asking if you wish
to zoom to the selected crashes.
Click on "Yes". The screen will redraw, zooming to the region
of selected crashes, as shown in Figure 8.
You may now proceed by selecting various parameters and producing reports,
as outlined in the AV-ALAS User's Manual. Additionally, if you wish
to zoom back to the previous zoom level, select View from the
menubar, then select Zoom Previous from this menu.
Additionally, you could, once the crashes have been selected, quickly
determine the number of crashes that have occurred in each year. This
can be done two ways.
First, you could select Theme from the menubar, then select
Table from this menu. This would result in a number of tables
opening, one for each year selected. When each table is made the active
table (i.e., the one in use at the time), the number of crashes selected
as well as the number of crashes total for that year will be displayed
in the upper left of the ArcView window.
Second, you could make each theme for each year active one at a time
and then select Request then Crash Locations for each
theme. The total number of selected crashes for that year would then
be returned.
Potential uses for box selections are numerous. They are the basis
for all further operations within ArcView ALAS whether you are selecting
a group of crashes or a group of nodes.
Spatial Query - Buffer Select
Engineering Task - Crashes within 1/4 mile of
an intersection
To begin, first proceed through the process to identify your region
of interest. That is, begin by selecting ALAS File from the menubar,
then select View Map from this menu. Proceed through the questions,
selecting the region type (County), the region desired (Story), the
timeframe of interest (1993-1997), and whether you want to use actual
crash locations or nodes for your selection (choose actual crash locations).
Once this has been completed, you should have a map showing Story County
roads, rails, rivers, and 1993-1997 crashes, shown in Figure 1.
Using the zoom-in tool, zoom to the Ames area (the large city on the
western edge of the map). First, move the mouse pointer to the zoom-in
tool button ()
and click with the mouse to select it. Then proceed by placing the zoom
button at one corner of a box that would contain Ames, pressing and
holding down the left mouse button, dragging the mouse to the opposite
corner of the box, and releasing the button. The box to be drawn (though
difficult to see) is shown in Figure 2. The resultant map should look
somewhat like the one shown in Figure 3.
Next, you either need to select the intersection of interest from a
current layer or you need to create a new layer containing an object
at the location of interest.
For either of these options the first step is to set the map and distance
units of the view. To do this, make sure the View (or map) Window is
active, then choose View from the menubar and Properties
from the menu. A dialog titled "View Properties" will appear,
shown in Figure 9. Note the Map Units and the Distance Units selection
boxes.
Change the Map Units to decimal degrees and the Distance Units to Miles,
as shown in Figure 10.
Additionally, it would be useful to zoom-in more to facilitate selection
of features.
To use a current layer for identifying the intersection of interest,
there are two options: using the crash layers if a crash has happened
at the intersection of interest or using the node layer because each
intersection should have a node. To use the crash layers to define the
intersection, use the box selection tool ()
to select the crashes that occurred immediately on top of the intersection.
To use the node layer to define the intersection, first activate the
node theme (named "Co. 85 Nodes") by moving the mouse pointer
to the node theme on the left of the map, click on it. Then, make the
the node theme visible by clicking on the small box to the left of the
node themes name. A check mark should appear in the small box and yellow
dots should appear on the map. Then, use the box selection tool ()
to select the node at the intersection of interest.
To create a new layer with an object that defines the intersection,
first select View from the menubar then New Theme from
the menu. A dialog box, shown in Figure 11, will appear, asking you
to identify the type of features contained in the theme. Select point
and click on the OK button.
Next a dialog box, shown in Figure 12, will appear asking you what
you wish to call the new theme and where you want to save it. Unless
you have a preference, just use the defaults and click the OK button.
Once you click OK, a new theme will appear and it will be active, visible,
and editable. To place a point at the intersection of interest, select
the draw point tool button (
).
Then move the crosshairs to the intersection of interest and click the
left mouse button. A new dot should appear, as shown in Figure 13.
To select this point, use the box selection tool ()
to select the point you just created.
Once you have set the map and distance units and used one of these
three methods to identify the intersection of interest, we can proceed
with capturing those crashes within 1/4 mile of the intersection. To
proceed, first make sure the crash layers for the years you are interested
in are active. If not, activate them by clicking on one of them, holding
down the shift key, and clicking on the others. Next, choose Theme
from the menubar and Select By Theme from the menu. A dialog
box will appear, shown in Figure 14.
Within this box, pick the theme from which you've identified the intersection
(in this case the creation of a new theme option, i.e, theme2.shp).
Then, under the heading "Select features of active themes that",
choose "Are Within Distance Of" and insert ".25"
in the box under the heading "Selection distance:" which will
appear. This is displayed in Figure 15. Then click the New Set button.
The results of the selection are shown in Figure 16.
You can then either "pan" the view to see the selection or
you can zoom to the selection. To pan, use the panning tool (
)
to move the map appropriately. To do this, select the tool, move the
mouse pointer to the map, click and hold the left mouse button, slide
the mouse pointer in the appropriate direction for the distance desired,
then release the mouse button. To zoom to the selection, choose View
from the menubar then choose Zoom to Selected from the menu.
You can get the total number of crashes selected by this process by
choosing Request from the menubar and Crash Locations
from the menu. Answers will appear as before.
Additionally, you may select multiple points simultaneously, create
multiple points within the new theme and select all of them, or use
other existing coverages (such as signalized intersection locations)
for your selection set.
Select Your Own
Using the tools described in this section, perform your own queries.
Please share your spatial query
uses with us so that we can add them to the available repertoire.
Mapping
Mapping of Selected Characteristics
Engineering Task - pin maps of animal-related crashes
To begin, first proceed through the process to identify your region
of interest. That is, begin by selecting ALAS File from the menubar,
then select View Map from this menu. Proceed through the questions,
selecting the region type (County), the region desired (Story), the
timeframe of interest (1993-1997), and whether you want to use actual
crash locations or nodes for your selection (choose actual crash locations).
Once this has been completed, you should have a map showing Story County
roads, rails, rivers, and 1993-1997 crashes, shown in Figure 1.
Once the Story County map is visible, you can proceed in three ways:
querying for animal-related crashes (either by using AV-ALAS functionality
or ArcView functionality), querying for animal-related crashes and viewing
only those crashes, or creating a thematic map.
To query for animal-related crashes countywide using AV-ALAS functionality,
once the county is open, select Search from the menubar, then
select Refine Search. A dialog box, as shown in Figure 17, should
appear.
From this dialog box select Crash Information and click OK.
Another dialog box, as shown in Figure 18, should appear.
From this dialog box, select Type of Crash. Another dialog box,
as shown in Figure 19, should appear.
From this dialog box, select Cancel as you want collision crashes
involving animals. A dialog box, shown in Figure 20, asking if you'd
like to Cancel All, Cancel Type of Crash: Non-Collision, or Don't Cancel
appears.
Select Yes from the choices as you only want to cancel the Non-Collision
selections. A new dialog box, shown in Figure 21, appears.
Select Animal from the list, then click OK. The code
will run for a bit, searching for all crashes for the years selected
within Story County involving animals, specifically crashes involving
collisions with animals. A dialog box, shown in Figure 22, will display
the answer.
Click OK. The final map should look like that shown in Figure
23.
If you watched the map redraw, you may have seen that some of the selected
crashes (i.e., the animal related crashes) were covered by non-selected
crashes. This makes the map less useful. To alleviate this problem and
get a map of just those crashes that were selected, you would want to
first use the city/county/region search capability in AV-ALAS. To do
this, choose Request from the menubar, then choose City/County/Region
Location from the menu. A dialog box appears, as shown in Figure
24.
From this dialog box, you could pick either county or region for our
purposes. Choosing county would result in another dialog box appearing.
This dialog box would list all counties available in the current view,
in this case Story County. From this list, you could pick the county
or counties you were interested in. However, choosing region would simply
select all crashes in all the counties currently open in the view. To
proceed with this example, choose Region. A dialog box, as shown
in Figure 25, appears, providing the total number of crashes for the
years available for the region.
Click OK. The view, as shown in Figure 26, shows all crashes
in the county as being selected (i.e., they are all red). Proceeding
through the above collision with animal crash procedure will now result
in the map shown in Figure 26.
Finally, the third option, thematic mapping, is covered in the next
section.
Thematic Mapping
Engineering
weather conditions
To begin, first proceed through the process to identify your region
of interest. That is, begin by selecting ALAS File from the menubar,
then select View Map from this menu. Proceed through the questions,
selecting the region type (County), the region desired (Story), the
timeframe of interest (1993-1997), and whether you want to use actual
crash locations or nodes for your selection (choose actual crash locations).
Once this has been completed, you should have a map showing Story County
roads, rails, rivers, and 1993-1997 crashes, shown in Figure 1.
To begin, move the mouse pointer to the left of the view where the
themes are listed, as shown in Figure 27.
Move the mouse pointer over one of the A Record themes, as shown in
Figure 28.
Double click the mouse. A dialog box, as shown in Figure 29, titled
"Legend Editor" will appear.
From this dialog, locate the "Legend Type:" selection area.
Choose Unique Value from the list. Then locate the "Classification
Field:" selection area. Choose Weather_co from the list.
The dialog should now look similar to that shown in Figure 30.
For weather conditions, the codes within the columns are as follows:
1 - Clear
2 - Cloudy
3 - Fog
4 - Mist
5 - Rain
6 - Sleet/Hail
7 - Snow
8 - Strong Wind
9 - Other
0 - Unknown
Up to two values may entered for each crash, therefore most crashes
have two values (i.e., 27 = Cloudy and Snow). Of these, Snow has the
highest precedence, followed by Sleet/Hail, Rain, Mist, Fog, Strong
Wind, Cloudy, Clear, Other, and, finally, Unknown. Knowing this, we
can assign symbols, colors, and labels to the values. To do this, first
locate any value in the list which contains a 7 (i.e., Snow). Now set
each of the symbols for these values to a large, blue snowflake. To
do this, double click on the colored dot 
to the left of the value under the Symbol heading. Another dialog box,
as shown in Figure 31, will appear.
Then, with the marker button (
)
depressed (
),
search for and select the snowflake from the marker symbol list, as
shown in Figure 32.
Now, set the size to 12, as shown in Figure 33.
Then, with the color button (
)
depressed (
),
search for and select a medium blue (
)
by double-clicking on the blue, as shown in Figure 34.
Then, on the "Legend Editor" window, click on Apply.
The View should change accordingly.
Remember to repeat this process for all those values that contain a
7 (i.e., Snow). Next, do the same for all values containing a 6 (i.e.,
Sleet/Hail) but not a 7. However, instead, use a different symbol, size,
and/or color (e.g., make the symbol smaller but leave the symbol and
color the same). Use a size of 8 for this exercise, but leave the symbol
and color the same as for Snow. Repeat this through the hierarchy of
weather conditions. You must do this for each year. Additionally, it
is useful to select all values that will have the same symbol by holding
down the CTRL key on the keyboard and clicking on each one of
these values. This saves time by allowing you to change the symbols
of all these values simultaneously. Some suggested symbols follow:
7 - Snow: 
6 - Sleet/Hail: 
5 - Rain: 
4 - Mist: 
3 - Fog: 
8 - Strong Wind: 
2 - Cloudy: 
1 - Clear: 
9 - Other: left colorless
0 - Unknown: left colorless
Finally, you might want to label each of these values. To do this,
click under the label heading and insert a new value. Some labels that
have been entered are shown in Figure 35.
You can label any way you choose. The convention used for labelling
here was first value name/second value name (i.e., 27 = "Cloudy/Snow"
while 72 = "Snow/Cloudy").
The final view should look like that shown in Figure 36.
access management scenarios (e.g., broadside/left
turn)
To begin, first proceed through the process to identify your region
of interest. That is, begin by selecting ALAS File from the menubar,
then select View Map from this menu. Proceed through the questions,
selecting the region type (County), the region desired (Story), the
timeframe of interest (1993-1997), and whether you want to use actual
crash locations or nodes for your selection (choose actual crash locations).
Once this has been completed, you should have a map showing Story County
roads, rails, rivers, and 1993-1997 crashes, shown in Figure 1.
To begin, move the mouse pointer to the left of the view where the
themes are listed, as shown in Figure 27. Move the mouse pointer over
one of the A Record themes, as shown in Figure 28. Double click the
mouse. A dialog box, as shown in Figure 29, titled "Legend Editor"
will appear. From this dialog, locate the "Legend Type:" selection
area. Choose Graduated Color from the list. Then locate the "Classification
Field:" selection area. Choose Collision_ from the list.
The dialog should now look similar to that shown in Figure 37.
For collision types, the codes within the columns are as follows:
1 - Head-on
2 - Broadside/Left Turn
3 - Rear End
4 - Rear End/Right Turn
5 - Rear End/Left Turn
6 - Sideswipe/Opposite Direction
7 - Sideswipe/Same Direction
8 - Sideswipe/Right Turn
9 - Sideswipe/Left Turn
10 - Sideswipe/Dual Left Turn
11 - Sideswipe/Dual Right Turn
12 - Broadside/Right Angle
13 - Broadside/Right Entering
14 - Broadside/Left Entering
15 - Head-on/Left Entering
16 - Sideswipe/Both Left Turning
17 - Other
18 - Single
19 - Pedestrian
20 - Bicycle
Knowing this, we can assign symbols, colors, and labels to the values.
To do this, first we will limit the number of classification fields,
as we are only interested in Broadside/Left Turn crashes. Click on Classify.
A dialog, shown in Figure 38, titled "Classification" appears.
Select "Number of classes:" equal to 3 and click OK.
The "Legend Editor" should now look like that shown in Figure
39.
Now, to show only Broadside/Left Turn Crashes, set the ranges and symbols/colors/sizes
to denote those you want to show vs. those you don't (i.e., set the
first range as 1, the second as 2, and the third as 3-20) as shown in
Figure 40.
Click Apply. The View should now look like that in Figure 41.
Repeat this for the other years.
Select Your Own
Using the tools described in this section, perform your own queries.
Please share your mapping uses
with us so that we can add them to the available repertoire.
Data Integrations
integration with road data
Engineering Task - rate based on VMT
In order to perform the necessary functions to determine a rate based
on VMT, you will now need to do some set up on the data files. Currently
they are uneditable because they came off a CD or are on a CD. They
need to be editable. If they are one a CD, you need to first copy them
from the CD to your hard drive. Place them under the _avalas directory
under this path "_avalas\_maps\_county\_", where
equals the name of the county you are copying (e.g., Boone
county data files would be under "_avalas\_maps\_county\_boone").
Start with an underscore ("_"), only use 8 total characters,
and place underscores ("_") between words. Once the files
are on the hard drive in the proper place, you must set their properties
so that they are editable. To do this, begin by opening Windows Explorer
by moving the mouse pointer to the lower left of the screen, clicking
on Start and then clicking on Windows Explorer, as shown
in Figure 42.
Now, locate the data directory on your computer, perhaps "c:\_avalas\_maps\_county\"
or "d:\_avalas\_maps\_county". For this example, "e:\_avalas\_maps\_county\"
was used, as shown in Figure 43.
Then locate the county of interest (if multiple counties, repeat this
as needed) and select it. In this case, select Story as shown in Figure
44.
The files listed in your Explorer window should be similar to those
shown here. Now select all the files in the directory by clicking on
the first file, holding the shift key down, scrolling to the bottom
of the files, and selecting the last one. This is shown in Figure 45.
Next, while the mouse pointer is over one of the selected files, click
the right mouse button. A screen like that shown in Figure 46 should
appear.
Now click on Properties. A dialog box like that shown in Figure
47 will appear.
Note that the Read-only and Archive boxes have checkmarks in them.
Click on the boxes to remove these checkmarks. The window should now
look like that shown in Figure 48.
Now click Apply. The window will now look like Figure 49.
Click OK. Remember to repeat this process for each county of
interest.
Note: You will want to be very CAREFUL
about file saving now that you have made these files editable. Remember
that you have the data on CD if you happen to save over a file. There
is potential for accidentally doing so. You might consider saving these
files to another directory after you finish this process and reloading
the CD files for future analyses. This would be advisable due to the
high risk of biasing future analyses.
Now that the files are editable, you can proceed.
To begin, first proceed through the process to identify your region
of interest. That is, begin by selecting ALAS File from the menubar,
then select View Map from this menu. Proceed through the questions,
selecting the region type (County), the region desired (Story), the
timeframe of interest (1993-1997), and whether you want to use actual
crash locations or nodes for your selection (choose actual crash locations).
Once this has been completed, you should have a map showing Story County
roads, rails, rivers, and 1993-1997 crashes, shown in Figure 1.
Next, move the mouse over to the roads theme layer on the left side
of the view and click. Then, while holding the shift key down, click
on each of the A Record crash themes. The view should look like that
in Figure 50.
Then select Theme from the menubar and choose Table from
the menu. A number of tables should open, one for each active theme
(in this case, 6) as shown in Figure 51.
A list of the tables appears in the project window, as shown in Figure
52.
You can close the open table windows by clicking on the close window
"X" (
)
in the upper right of each table window. Do this. To open each table
up again, simply double click on its corresponding listing in the project
window. Open the roads table and the 93 A Records table and move them
apart so that you can see them both (do this by placing the mouse pointer
on the title bar, clicking and holding the left mouse button and moving
the mouse to the position desired, then release the mouse button when
the window is in position). Resize the table windows if you desire (to
do this, place the mouse pointer on an edge of one of the tables, click
and hold the left mouse button, move the mouse to the position desired,
then release the mouse button when the window is the size desired).
You don't have to move them and resize them, but it generally makes
things easier to comprehend. Figure 53 shows the windows moved and resized.
Across the top of each table you see column headings. Both tables have
Shape columns, one with PolyLines and one with Points. The rest of the
data is specific to each table. Each A Record table will have the same
column headings, however.
To begin the actual formulation of the rate based on VMT, you must
first determine which links each link crash is associated with (we limit
this example to links as intersections are more complex). To do this
we perform a spatial join. That is, we use the spatial nature of our
data to associate those roadway links (i.e., each row in the roads table)
with those crashes (i.e., each row in the A Records tables) that fall
upon them. We do this step so that we can create a unique identifier
for each crash that identifies which roadway it is closest to.
First, though, we must limit our crashes to just link crashes. To do
this, click on the title portion of the A Records table. This table
is now the active table. Then click on the Query Builder tool button
(
). A dialog
box, shown in Figure 54, titled "Attributes of Co. 85 Yr. 1993
A Rec." will appear.
Now, find the "[Dir_node]" listing under the "Fields"
heading. Double click on this. It will appear in the box below. Now
click on the "<>" button (
)
and it will appear as well. Then either type in 999999 or find it and
double click on it in the right list under the "Values" heading.
The window should look like Figure 55.
Then click on the "New Set" button (
).
Close the window by clicking on the "X" ()
in the upper right of the window. The A Records table should now have
roughly half its rows highlighted in red (i.e., all rows with a Dir_node
column value not equal to 999999 should be highlighted). This is shown
in Figure 56.
Now click on the switch selection button (
)
to select all crashes but the link crashes. (Alternatively, you could
have simply used the "=" button (
)
in the query statement to select the intersection and node crashes.)
Switching the selection causes all the non-link crashes to be selected.
You need to do this because now you are going to delete all the selected
crashes and, as you are interested in retaining the link crashes, you
need to have them unselected. To delete the selected crashes, you first
need to make the table editable. To do this, click on Table in
the menubar and select Start Editing from the menu. The table
will change slightly (i.e., the column headings are now not italicized).
Now click on Edit in the menubar and select Delete Records
from the menu. The selected records should be removed after a short
wait (the wait will depend on the size (number of records) of the table
and the number of records selected). Now no records should be selected
in the table. To save the edits you just made, select Table from
the menubar, then choose Save Edits As... from the menu. A dialog
box, as shown in Figure 57, will appear which allows you to name the
table.
You may choose any name and any destination directory you choose, however,
it is advisable to name the file meaningfully and place the file somewhere
easily remembered. For this example, name it links.dbf and put it under
your _avalas\_reports\ directory, as shown in Figure 58.
Now, the original table will have all its records back and not be in
edit mode. Additionally, a new table, titled "links.dbf" will
have appeared and be in edit mode and be active. This is shown in Figure
59.
Now add a field to this table. To do this, select Edit from
the menubar and then choose Add Field. A dialog box, shown in
Figure 60, will appear.
integration with other data
Engineering Task - signalized intersections
To begin, first proceed through the process to identify your region
of interest. That is, begin by selecting ALAS File from the menubar,
then select View Map from this menu. Proceed through the questions,
selecting the region type (County), the region desired (Story), the
timeframe of interest (1993-1997), and whether you want to use actual
crash locations or nodes for your selection (choose actual crash locations).
Once this has been completed, you should have a map showing Story County
roads, rails, rivers, and 1993-1997 crashes, shown in Figure 1.
Share your uses.
