1. Chapter 2: Solving Traffic Safety Problems
Overview
Problem Solving
Information Gathering
Identifying Contributory Factors
Selecting the Appropriate Countermeasure
Evaluating Success
Prioritizing Improvements
Because road agencies usually have limited funds with which to meet a growing number of projects, your safety goal should be to apply the right solution to the right problem on the right road at the right time. This is why problem solving and planning are important.
The first goal for improving road safety is to stop crashes before they happen. By removing the problem, you may be able to prevent crashes. The second goal is to reduce the seriousness of crashes when they do happen.

2. Problem Solving Technique
1. Identify problem
2. Select appropriate countermeasure
3. Install countermeasure
4. Evaluate countermeasure effectiveness
5. If not effective, return to Step 1
Step 1: Correctly identifying the problem is the most important step in solving safety problems. If you apply the wrong solution to the identified problem, you have just wasted time and money.
Step 2: Remember why step 1 (problem solving) is so important -- the best countermeasure will not solve the wrong problem. Be sure that the selected countermeasure will not move the safety problem to a different location. Also, consider the cost of the countermeasure (low-cost safety improvements may be equally effective as expensive improvements).
Step 5: Why return to step one? Why not just pick another countermeasure? Answer: You may not understand the problem.

3. Information Gathering
Identify the problem?
Define what’s causing it?
Information sources
Remember why step one in problem solving is so important: The best countermeasure will not solve the wrong problem. Gathering information, the right information, will help you identify the real safety problem. Traffic safety studies are a good way to collect information related to road conditions or traffic characteristics.

4. Look for commonalities
What is the Problem?
Describe symptoms
Right-angle crashes at intersection
Crashes happen on rainy days
Look for commonalities
They often point to the cause

5. Emergency medical service Crash records
Information Sources
Public
Police
Emergency medical service
Crash records
Go out and look (site inspection)
Sources of information:
The public
a. Prior notice
b. Suggestion may be wrong. That doesn’t mean there is not a problem
Emergency services
May notice accident pattern
Police & prior notice
Superintendent and crew: Keep your eyes open. Regular patrols & after storms, etc.
Accident analysis (Crash records)
Can give best picture
Takes years for patterns to develop – especially on low volume roads
People may have already been hurt before you have enough crash data to do the study.
Road safety audits
RSA’s proactive, not reactive – find deficiencies before a crash happens.
May miss something that would show up as an accident pattern

6. Condition Diagrams Can anyone spot a safety hazard on this diagram?
Trees on outsides of curves
Utility pole in front of guardrail
Signs improperly placed
Pines may cause sight distance problem at intersection
Unprotected headwall
What if you do the diagram, and it gets subpoenaed?
- have a plan for correcting any safety deficiencies you may find
- execute the plan.

7. Collision Diagrams Identify common crash types or conditions
Need police crash reports to construct
May require several years of crash records
A collision diagram can be a useful tool for identifying common crash types or conditions that frequently exist during crashes at intersections or on road segments. To prepare a collision diagram, you will need to know the layout of the intersection or the road segment. You will also need the police crash reports to construct the diagram.
The graphic shows the vehicle movement and crash severity; crash type, date, and time; and identification number for each incident.
Understand that there are some serious drawbacks to crash analysis. First, you need enough quality data to get a good perspective on the area and its problems, but you cannot conduct an analysis until several years after a project has been completed. More importantly for local jurisdictions, a crash analysis will not work as well on low-volume roads. Rather than 3 years of crash data, you may need 10 years or more before a pattern emerges.

8. Crash Mapping Right-angle Rear-end Run-off-road Left turn Pedestrian
Head-on
Gathering crash data, looking for patterns.
The pattern may not be a crash type – could be wet pavement, a particular time of day, etc.
May take 10 years of data for a pattern to show up, especially on low volume roads.

9. Road Safety Audits
Formal safety examination by independent review team
Proactive approach to look for potential safety problems
Can take place at any stage of project
Audit teams rank urgency of safety defects
Always document safety issues and develop a plan to address them
A road safety audit is a formal examination of the safety performance of an existing or future road or intersection by an independent audit team. Following the assessment, the team prepares a brief report identifying potential safety issues. The jurisdiction owning the road or intersection then responds to the problems identified and determines the action(s) it will take, or documents the reason for not acting on a suggestion. Road safety audits of existing roads are sometimes called road safety audit reviews.
We say that road safety audits are proactive because the team looks for potential safety issues before someone is injured or killed. Road safety audits can take place at any stage of a project, or on existing roads. The team audit report usually ranks the urgency of defects found. The team may give a low-priority rating to a location where a crash is unlikely, but a serious defect that potentially could cause frequent or severe crashes would receive a high-priority rating. These priorities provide road departments with a cost-effective way to evaluate problems and focus resources wisely.

10. Does a road condition contribute? Traffic control? Road conditions?
What’s Causing It?
Does a road condition contribute?
Traffic control?
Road conditions?
Could a change to the road help?
Prevent driver error?
Provide room to recover?
Reduce severity?
Identifying the cause of a crash pattern is like putting together pieces of a puzzle. Sometimes the pieces fit easily. Common examples are run-off-road crashes on the outside of a curve, or wet pavement crashes.
To find patterns, look for similarities between crashes: Similarities in types of crashes, weather patterns, or other contributing factors can provide valuable clues as to why crashes occur. Several highway agencies have developed go bags for collecting evidence at crash sites. Go bags usually include camera, notepad, and safety vest. Other necessary go-bag gear includes plastic zip-loc bags with labels for collecting evidence, stop watch, flashlight, calculator, spray paint, hand level, measuring wheel, 100-ft tape measure, stringline, nails, hammer, and orange traffic cones.

11. Selecting Countermeasures
What kind of crashes are you trying to prevent?
For example, rear-end or wet weather
Choose the one that best fits problem
Watch for unintended consequences
Example:
Potential causes of rear-end collisions include: poor sight distance on approach to intersections, poor traffic signal timing, left-turn traffic yielding to opposing through traffic. Poor sight distance issues can be addressed by installing stop ahead or yield ahead signs. Revised signal timings (green or yellow phase) can reduce rear-end crashes if signal timing is an issue. Left-turn lanes can reduce rear-end collisions associated with left-turning traffic.

12. Install Appropriate Countermeasure
Understanding what factors create a problem is the key to finding the right solution. The solution, or countermeasure, should target a particular crash type or contributing factor. Remember, the goal is to reduce the number and severity of crashes while understanding that no one solution solves all safety problems and no one countermeasure works for all types of crash patterns.
Some transportation agencies publish crash reduction factor lists that describe the rate you can expect a given countermeasure to reduce crashes. In one example, adding arrow signs or chevrons to a bad curve reduced run-off-road crashes by 34 percent.
Use appropriate work zone traffic control when installing the appropriate countermeasure because this typically involves construction.

13. Is It Working? Before and after study Observe traffic
May need to try again
You want to make sure that what you did is helping. You can wait a few years, and compare crashes before the improvement to crashes after, or watch traffic and look for a change in driver behavior.
Be sure to use an appropriate evaluation technique if comparing before and after crash experience.
Questions?

14. Evaluate Effectiveness Example
Right -
angle
Rear
end
Run
off
road
Left turn
Pedestrian
Head on
This is an animated slide. At first, you see the original crash mapping graphic. Then a second crash mapping graphic fades into the slide with less crashes at several intersections. Indicate to the participants that safety improvements were made at several intersections in the study area – the first view of the study area is the “before” period and the second graphic is the “after” period. Once could conclude that the safety improvement program is effective based on the reduced crash frequency.

15. Prioritize Work Do what you can, where you are, with what you have.
– T. Roosevelt

16. Priority Levels Urgent - immediate attention needed
High - improve in the near future
Medium - improve as priority allows
Low - improve when other work is done to road
Organize safety problems by location, in the following order:
Frequent or severe crashes occur.
Crashes occur occasionally.
Crashes are rare.
Next, consider how to rate crashes. Crash severity refers to how bad the crashes are, such as fatal, serious, or minor. Severity is the result of speed and the type of crash. Crash probability indicates how often you expect crashes to occur in the future. Use the crash history of a location to find probability. When you combine severity and probability, you can identify a priority. It follows that locations with frequent, severe crashes should have the highest priority. Likewise, give locations with few minor-crash patterns a low priority. Rare severe crashes and frequent minor crashes are in between. The graphic on the next slide illustrates the concept described.

17. Priority SEVERITY FREQUENCY Frequent Occasional Rare Fatal Serious
URGENT
HIGH
MEDIUM
Serious
LOW
Minor
Base on accident history, if you have one.
If not, it requires a judgement call.
Probability goes up with traffic volume, on curves, at intersections
Look for places with more than one contributing roadway factor: intersections on with poor sight distance, for example
These accidents tend to be severe:
Fixed object
Pedestrian
Head-on
Right-angle

18. Other Priority Factors
Right-angle
Rear-end
Run-off-road
Left turn
Pedestrian
Head-on
Which intersection comes first?
Why?
Which one is easier to fix?
Which is cheaper?
Traditionally, we would go after the lower intersection first, since it has the worse crash history. However, the upper intersection may be easier to solve.

19. Think Long Term
Development leads to traffic. Traffic leads to crashes. Low priority items will become problems. When an area starts to develop, start looking for and addressing these conditions that will become problems as traffic increases.

20. Think Long Term
According to last inspection, this bridge has 10 years useful life in it. It also has very poor geometry – an 80 degree delta, 40' radius turn on the far side. This superintendent has already started grading to install the new bridge on a better alignment. With his annual budget, he has to.
Can’t fix everything overnight
Include safety in other projects
Try one safety project per year

21. Documentation Defense against litigation Highway defect complaints
Patrols and condition surveys
Sign inventories
Traffic studies
Good documentation of a thoughtful road safety improvement program is your best defense against liability.
You should document highway defect complaints, condition surveys (pavements), sign inventories, and traffic studies.

22. What, Where, When, Who, Why, How Document even if no defects found
What to Document
What, Where, When, Who, Why, How
Document even if no defects found
Get all the details!
If you can show that there wasn't a problem as of a certain date, then you can counter claims of constructive notice when a crash occurs soon afterwards.

23. Problem solving procedure Prioritizing safety improvements
Summary
Problem solving procedure
Prioritizing safety improvements
Documentation
Stress the importance of documentation. Documentation supports the validity of a prioritized safety improvement plan.
The steps to appropriate documentation include:
Identify the site with a safety problem.
Visit the site and record important conditions, including intersection dimensions; road segment, signs, pavement markings; number of lanes and lane width; available clear zone; horizontal curvature and grades; and lighting conditions.
Research and record the crash characteristics including number of vehicles, crash type, day of week, time of day, vehicle speeds, and the crash location.
Prepare a report of the findings (include photographs).
Select an appropriate countermeasure and record the reason for choosing it.
Evaluate countermeasure effectiveness and report the findings.