Prioritizing Work


One of the hardest parts of developing a highway safety improvement plan is deciding where to start. At all levels of government from the smallest village up to the Federal Highway Administration (FHWA), the available funds are exceeded by the needs. Like road surface management, drainage, and everything else a highway department does, safety improvements need to be prioritized to make the best use of limited resources. Could a list of prioritized safety improvements cause…... Read more

Evaluating Success


After installing a countermeasure, make sure it is working. If you had a history of accidents before the change, compare the accident frequency before the change to the frequency afterwards, and see if it went down. If it did not, look into other countermeasures. You may find unintended consequences. For example, prohibiting left turns at an intersection may increase the number of left turn accidents at the next intersection. If the number of accidents prior…... Read more

Selecting a Countermeasure


Understanding what factors are contributing to accidents is the key to countermeasure selection. The countermeasure should be targeted at a particular crash type or contributing factor. The goal is to reduce the number and severity of accidents that occur. There are no cure-alls for safety problems. No countermeasure works for all types of accident patterns. Traffic signals, for example, do not always reduce the number of accidents. They usually reduce the number of right-angle accidents…... Read more

Identifying Causes and Contributing Factors


Identifying the cause of an accident pattern is like putting together pieces of a puzzle. Sometimes the cause of an accident pattern will be obvious. Run-off-road accidents on the outside of a curve, or wet pavement accidents are common examples. Other times, the problem can be subtle. One case involved a nighttime accident pattern at the state line. Until an investigator happened to drive across the state line at night, no one realized that there…... Read more

Information Gathering


The best countermeasure will not work if it is used for the wrong problem. We have to gather the right information to understand the problem to get the best results. Information used in traffic safety studies is usually related to road conditions or traffic characteristics. Condition diagrams Condition diagrams are drawings, more or less to scale, that show the locations of curves, traffic control devices, fixed objects, etc. An example of a condition diagram is…... Read more

Identifying and Solving Problems


Because of limited resources, we need to apply the right solution to the right problem on the right road at the right time. This is where problem solving and planning come in. When improving road safety, the first goal is to stop crashes from happening. That is why the emphasis for roadside improvements is on removing hazards rather than installing guiderail. The second goal is reducing the severity of accidents that do happen. When a…... Read more

Opportunity Cost


You might wonder whether a traffic improvement plan is worth the cost and effort. That time and money could go into making improvements, rather than just planning them. The opportunities you give up when you choose an option are called the opportunity cost. If you choose to spend part of your budget on rebuilding a road, the opportunity cost is everything else you could have done with that money, but chose not to. Consider the…... Read more

Combination of Factors


Detailed investigations of man-made catastrophes often show a chain of events leading to the incident. It is said that an incident happens when nine things go wrong, and a catastrophe occurs when ten things go wrong. Often breaking a link of the chain of events can prevent an accident. Highway crashes are no different. In most cases where a road condition is involved in an accident, a driver factor also contributes to the crash. For…... Read more

Roads and Their Environment


To design a road to fit the needs, we need to know how it is used. These traffic characteristics include the types of traffic on the road, how many use the road on an average day, and how fast they travel. Functional class Roads are classified based on the role they play in the transportation network: Local roads primarily provide access to adjacent land. Through-traffic is usually a small per- centage of total traffic. Collectors…... Read more

Road Safety Basics


To reduce traffic accidents, we need to understand what causes them. The highway transportation system can be broken down into three broad categories: the driver; the vehicle; and the road and its environment. Factors that help cause accidents usually fit into one of those categories. Most accidents have at least one contributing factor. Many have several. Human factors include things like inattention or distraction, fatigue, alcohol use, and vision problems. Vehicle factors may be mechanical…... Read more

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