Highway Fatality Database Created in ArcView 8 for Eight Counties in Southwest South Dakota From South Dakota Department of Transportation Data, 1983-2001

Here are some analytical charts I made in ArcView 8 and Excel demonstrating a few questions that can be answered based on the highway fatality data supplied by the South Dakota Department of Transportation for Shannon, Bennett, and Jackson counties on the Pine Ridge Reservation, and the surrounding counties of Fall River, Custer, Pennington, Meade, and Lawrence.

Part of the work of creating this GIS database was accomplished during a GIS Research 393 course during Spring 2003 at Oglala Lakota College. Students who participated in that course were Michael Catches, Kyanne Dillabaugh, Adam Heriba, Justin Hooper, Cedar Lonehill, Dusty Mousseaux, Elvin Returns, and William Spoonhunter. In addition, Jane Sayler, at Sitting Bull College, completed the data entry for Pennington county during a Fall 2003 GIS Research 493 course.

Here is a map of the locations of all 684 fatal accidents which occurred in these 8 counties from 1983-2001.

And here is a chart showing how those accidents broke out for each county.

This GIS database has been formatted using descriptive terminology that will allow anyone to perform queries. I’ll give an example.

This screen capture shows how I select the accidents involving a pedestrian from the layer with all fatal accident data from 8 counties. The 8-county layer is called 8county_merge. The ACC_TYPE field contains the entries shown on the right, BICYCLE DRIVER, PEDESTRIAN, AND VEH/DRIVER. I created the expression ACC_TYPE = PEDESTRIAN and performed the query. The map shows the location of all the pedestrian accidents, 74 out of the total of 684.

Note the cluster between Pine Ridge and White Clay; this probably represents people walking down to White Clay to buy alcohol and coming back to Pine Ridge and being hit on the road. There is another cluster in the central Rapid City area.

Doing the search selects all entries from the 8county_merge layer that had PEDESTRIAN in the ACC_TYPE field. As shown at the bottom, that was 74 out of the 684 total fatal accidents entered here.

I can click the “Selected” button to view only these Pedestrian accidents, then I can save this out to a new layer.

I can do many analyses on this new Pedestrian layer since it contains all the data available for each of those 74 accidents. Here I’m going to summarize the accidents by county by summarizing the County column in the Pedestrian fatality attribute table.

I get the *.dbf table above showing the number of accidents by county which I import to Excel and graph.

Below is the chart of the pedestrian fatality data. Shannon and Bennett counties leads the pack.

In order to look at the influence alcohol may have had on either the pedestrian or the driver who hit him/her, I created the chart below. The pedestrian was under the influence of alcohol in 39% of these accidents; the driver in just under 26%. The difference is not large, but inebriated pedestrians are more common in these accidents than are drivers.

Below I summarized the alcohol related accidents by percent of total fatal accidents within a county. Using the percent of total accidents in each county ensures that we can make a valid comparison among different counties. Using actual numbers of alcohol related accidents would make more populous counties with more total accidents appear to have more alcohol related deaths, even though the percentage of total accidents might actually be higher in another county. The “rez” counties, Bennett and Shannon, have the highest percentage of accidents involving alcohol. Fall River and Pennington also shows an abundance of alcohol-related fatalities, >50%.

Next I analyzed the alcohol accident layer to determine the sex and age of inebriated drivers, combining data for all 8 counties. Below we see that males in the age group 20-39 are responsible for most of the alcohol related fatal accidents. Women drivers of any age group are not causing many of the highway deaths due to alcohol use.

Next I looked at fatal accidents in all 8 counties by time of day, taking accidents in 2-hour increments throughout the 24-hour period. The chart below shows the results. The chart is busy, but shows trends that can be further investigated.

Taking just the 3 reservation counties and charting the same time interval results, we see that both Shannon and Bennett counties have the most fatal accidents during the 4-6 pm and 6-8 pm hours. This probably relates to an increased volume of highway travel after school and work. Jackson county shows an anomaly of high fatal accidents during the 8-10 am period.

Taking 3 surrounding non-reservation counties and displaying the same data shows a different pattern. Here we see the anomaly of very high rates of fatal accidents in the Custer county data during the noon-2 pm time period. This seems to point to travel around the lunch hour in Custer, but indicates the importance of law enforcement monitoring of traffic very closely during this time period in order to prevent hazardous driving. Accident rates rise during the afternoon, as in Shannon and Bennett counties, but continue high during the nighttime hours in these counties, as opposed to the reservation. These data indicate that highway travel drops significantly on the rez at night but stays relatively heavy in these surrounding counties through midnight. It would be a good idea to keep patrolmen out on the highways during these evening hours in Custer, Fall River, and Pennington counties to try and apprehend the poor drivers out at this time.

Looking at time of day in which alcohol related accidents occurred in only Custer, Fall River, and Pennington counties, we see high rates of fatal accidents during the evening and early morning hours. Alcohol use and associated dangerous driving is not just occurring in the evening hours.

On the reservation, Bennett county shows a dropoff in fatal accidents at midday. Interestingly, all fatal accidents in Bennett county during 6 of the 7 2-hour intervals which had fatal accidents involved alcohol use. Shannon county has a very consistent rate of fatal alcohol accidents at all times throughout the day and night. Fatal accidents involving alcohol in Jackson county occur primarily during morning hours.

The next analysis looks at the accident data for all 8 counties by month of the year.

It is apparent that there is a very high rate of fatal accidents during August in Custer, Lawrence, and Meade counties. Those counties are graphed separately below. This significant spike during August represents the heavy motorcycle travel in these counties during the August rally at Sturgis in Lawrence county. Anyone living in the Black Hills of South Dakota knows of the massive volume of motorcycle traffic added to normal vehicle traffic during this month. These fatality data show clearly that the increase in motorcycle traffic results in higher highway fatalities around rally time and warrants all the attention that law enforcement can give to keeping highways safe at this season.

This graph shows the percent of total fatal accidents by county involving a rollover. Jackson leads the pack with 50% of accidents being overturns. The 2-lane roads without shoulders in the county, many of which have steep embankments falling off to the side, probably accounts for this problem as highlighted here.

The graph above shows the kinds of vehicles involved in fatal rollover accidents in the eight counties. Whereas 2WD sedans are most often involved in rollover accidents they actually are in fewer rollover accidents than in fatal accidents in general. However, notice that though the percentage of fatal rollover accidents involving 4WD SUVs is only 17%, that is twice the frequency of SUVs in fatal accidents overall, about 8%. This graph proves that SUVs are more prone than any other vehicle type to roll over in accidents in these 8 counties. While 2WD vehicles are not prone to roll over generally, the 2 lane roads with no shoulders which are common in these counties, as well as the steep banks on the sides of these roads, may have a strong influence on rollover accidents in these vehicles.

The frequency of seat belt use in accidents in which the driver died was less than 11% of accidents, but when the driver survived, over 25% were wearing seatbelts.

In accidents where the driver survived, 90% remained inside the vehicle. In accidents where the driver died, almost 36% were thrown completely from the vehicle. This would further indicate the importance of wearing seat belts and being held inside the vehicle during a crash.

The chart above shows the percent of fatal accidents by county over 4 periods from 1983-2001. It shows whether fatal accident rates are changing over time by county and where they were particularly high or low in the past. Custer shows a high fatal accident period from 1988-1992.

This graph shows only alcohol related fatal accidents during the same yearly periods. The high accident rate in Custer county during 1988-1992 appears to be strongly correlated with alcohol accidents. Fatal alcohol related accidents have been increasing in recent years in Bennett county.

These are just a few sample analyses to illustrate some of the information contained in this highway fatality database. For a copy of the database or to discuss it, please contact me at:

James Taulman

jtaulman@olc.edu

605-745-3959