Drug and Alcohol Involvement in
Pedestrian Injury Crashes in
Oregon

1 Introduction

Recently, ODOT raised a public safety question on how alcohol and drug involved crashes for pedestrians compare to motorized road users when controlled substances were involved. This question appears relatively straight forward, given that ODOT crash data carries a data element describing whether each crash had a user whereby drug or alcohol use was reported as a factor. The numbers were previously reported in ODOT’s recently completed Vulnerable Road User (VRU) Assessment. Based on the crash-level data, it was reported that 36.3% of fatal and serious (KA) crashes involved (a) someone walking and (b) the presence of drugs or alcohol(ODOT VRU 2023). However, I, as an analyst have always wondered how, by looking only at the crash level data, we obscure which crash participant was reported as alcohol or drug involved, so decided to take a closer look at this question of drug and alcohol involvement in pedestrian crashes by unpacking who was reported as using one of these controlled substances at the time of the crash.

2 Data Definitions

This brief analysis started by defining a few terms including what is meant when the term alcohol or drug involved is used since those definitions come from the ODOT Crash Data Manual, an excellent document with all the details of explaining how ODOT constructs and classifies crashes in Oregon. Definitions from the crash manual are as follows:

• Alcohol Involved: Police report that participant had been drinking; or suspect admits it
• Drug Involved: Participant had been using drugs (Reported by police, test results, or suspect admits it)

When alcohol or drug involved (ADI) is referenced, its not necessarily saying legally impaired as that has to do with results of blood alcohol content (BAC) test result or result of a test from a drug recognition expert at the scene of the crash. The below summaries are only discussing ADI crashes.

3 Data Preparation

As mentioned above, often what is reported for ADI crashes comes from the crash level data which in the case of pedestrian crashes masks whether the driver, the pedestrian, or both road users were reported as ADI. In order to understand which road user is ADI in the crash analysts must use the crash participant(or person) level crash information which shows what was recorded for each road user type in terms of ADI. We then code the crash in a typology as follows:

• No alcohol and/or drugs involved
• Pedestrian only alcohol and/or drugs involved
• Driver only alcohol and/or drugs involved
• Pedestrian & Driver drugs and/or alcohol involved

Lastly, the information presented below includes two road users type categories and are defined as follows:

• Pedestrian: included person walking, using a pedestrian conveyance device(wheelchair, skates, etc.) or pedestrian towing object, other participant, conveyance
• Motor vehicle: driver of a passenger vehicle, motorcycle, or freight vehicle

4 Analysis

Presented below is a chart that shows the percentage of total fatal & serious injury crashes that involve alcohol and/or drug by road user type for the last five years of available data. This chart shows that for motor vehicle driver only fatal and serious injury crashes, between 2018 and 2022, 24.2% were alcohol and/or drug involved. Now the interesting part: traditionally it would be reported that for pedestrian involved fatal & serious injury crashes, 36.9% have alcohol and/or drug involvement which is presented in the blue bar below. One issue here is that this combines ADI status based on both the driver and pedestrian being reported as ADI. Given these are pedestrian crashes it might imply that the pedestrian only was the ADI user. Using the typologies described above we break out the crash data by whether it was just the pedestrian (orange bar) that was ADI or the pedestrian and the driver (in the same crash) in the tan bar who was ADI. Looking at instances where just the pedestrian was an ADI participant the percentage of pedestrian fatal and serious injury crashes that are ADI drops is 26.6% (orange bar) rather than 36.9%. If we count the crashes where both (in the same crash) the driver and the pedestrian were ADI then the figure is 32.1%.

Figure 4.1: Alcohol and Drug Involvement in Fatal & Serious Injury Crashes

The chart in Figure 4.2 shows the ADI involvement in pedestrian fatal and serious crashes over time. This figure shows that compared to motor vehicle driver only ADI crashes, pedestrian crashes where only the pedestrian is ADI is on average about 3% different. One notable trend in these data is the increase over time of the proportion of crashes that are ADI. For the first five years (2002-2006) the proportion of pedestrian crashes that were ADI was about 16% as was the motor vehicle driver average proportion for those five years. However, by the latter part of the time series the five year average was up to 28% for pedestrian only and 24% for motor vehicle drivers respectively. This rise in ADI status for road users involved in crashes is problematic and challenges transportation authorities in Oregon looking to reduce serious and fatal injuries. Lastly, in 2022 there was a 6% increase in the pedestrian only ADI from 2021 while the motor vehicle driver ADI decreased.

Figure 4.2: Alcohol and Drug Involvement in Fatal & Serious Injury Crashes Over time

To make the comparison easier for readers, the table below shows the percentages presented above side by side for closer visual examination. To test if there is any meaningful difference between the Pedestrian Only and the Motor Vehicle Driver we can use a simple Student’s t-test which is a statistical test that compares values between two groups. When comparing the Motor Vehicle Driver column with the Pedestrian Only column the t-test shows that no statistically significant different exists.

	Alcohol and/or Drug Involved User
Year	Motor Vehicle Driver	Pedestrian Only	Both Pedestrian & Driver or Pedestrian Only	Either Driver or Pedestrian or Both
2002	%	13%	13%	19.6%
2003	%	18.5%	19.2%	22.6%
2004	%	9.8%	12.3%	20.5%
2005	%	16.4%	19.9%	23.4%
2006	%	21.1%	24.4%	27.8%
2007	%	22.1%	25.3%	31.2%
2008	%	24.1%	29%	35.2%
2009	%	19.8%	21.4%	27%
2010	%	26.1%	30.1%	37.3%
2011	%	23.9%	25.8%	31.9%
2012	%	27.1%	33.5%	42.4%
2013	%	23.5%	28.9%	36.9%
2014	%	17.8%	22.7%	28.8%
2015	%	18.6%	24%	33.3%
2016	%	23.2%	28%	33.3%
2017	%	26.1%	28.3%	36.4%
2018	%	25.9%	31.7%	37%
2019	%	29.1%	34.2%	38.7%
2020	%	27.1%	31.2%	37.7%
2021	%	24.9%	28.2%	32.5%
2022	%	32%	35.3%	38.5%

5 Final Thoughts

This short report highlights a quick analysis the ODOT Research Unit performed for fellow ODOT staff to document the percentage of fatal and serious pedestrian crashes that are alcohol and/or drug involved. To answer this question we aimed to tell a fuller story that underscores the importance of considering which participants involved in pedestrian crashes are reported to have been using alcohol and/or drugs. Reporting the traditional measure where the ADI proportion for pedestrian crashes is 10-plus points higher than motorized driver crashes skews the comparison and could be used to support a narrative where the pedestrian is more at fault than the motorized vehicle user. This report also highlighted the rise in ADI for both driver and pedestrian crashes over time. This increase in ADI crashes challenges transportation authorities seeking to reduce traffic injury in Oregon. A lot more could be said on this topic and certainly more work needs to be done.