Intersection Safety Implementation Plan Process

< Previous Table of Contents Next >

Step 1: Set the Intersection Crash Reduction Goal

Many State SHSPs define overall statewide safety goals. However, most SHSPs do not define the portions of the goal to be addressed by emphasis area such as improving intersection safety, reducing roadway departures, improving pedestrian safety, reducing drinking and driving, and preventing aggressive driving. Because SHSPs often do not contain this level of detail, the number and types of countermeasures within an emphasis area needed to help achieve the overall goal can not be ascertained. This can result in less focus on deployment levels, costs, and statewide fatality reductions associated with the implementation of strategies and countermeasures.

The overall SHSP goal may be expressed in terms of reductions in fatalities or some combination of fatalities and injuries by a certain time. It may also be expressed in terms of a reduction in the rate in crashes or fatalities per million vehicle miles traveled (VMT) or per 1,000 population. Two examples of setting an intersection goal that is aligned with the SHSP goal are provided.

Example 1 – SHSP Goal as a Reduction in Absolute Numbers

If the SHSP goal is established in terms of a reduction in absolute numbers of fatalities and/or injuries by a given date, then information on the past trend of those fatalities and/or injuries is needed.

Assume State B also had 1,000 fatalities in 2007, 200 of which were intersection or intersection-related. State B has a goal to reduce total fatalities to no more than 850 by 2013. Over the past several years the fatalities have fluctuated as shown in Table 1.

Table 1: Sample Fatalities for State B
Year Fatalities
2007 1,000
2006 923
2005 975
2004 1,021
2003 1,064

In 2013, it is expected that 9401 fatalities will occur. Additional strategies and efforts that result in 902 fewer fatalities are needed to achieve the goal. The intersection portion of that goal is 20 percent of 90, or 18 fewer intersection deaths annually.

Example 2 – SHSP Goal Expressed as a Reduction in Rate

If the SHSP goal is expressed as a rate, it is important to convert the rate to an expected reduction in fatalities and/or injuries by the time the goal is to be achieved. Two pieces of information are needed to properly make this determination:

  1. The fatality rate for each of the last 5 years of data.
  2. The expected annual change in VMT for each year up to the year in which the goal is expected to be achieved.

Using the data from the last 5 years, the trend in the fatality rate can be estimated. The trend can predict the expected fatality rate in the year the goal is to be achieved. Then, using the predicted fatality rate and the estimated VMT in the goal year, the expected number of fatalities can be estimated.

As an example, assume that State A had 1,000 fatalities in 2007, 200 of which were intersection or intersection-related. State A also has a goal to reduce the fatality rate from 1.30 in 2007 to 1.00 in 2013. The fatality rates over the past several years are provided in Table 2.

Table 2: Sample Fatality Rates for State A
Year Fatality Rate per VMT
2007 1.30
2006 1.34
2005 1.37
2004 1.41
2003 1.45


Table 2 shows that the fatality rate is declining at an average rate of approximately 3 percent annually. Projecting ahead, the expected fatality rate in 2013, assuming current trends continue and no added improvements are implemented, would be 1.12.3 However, over the next 6 years VMT is expected to grow at a rate of 2.3 percent annually, or 13.8 percent over 2007 VMT. The statewide VMT for 2007 is 76.9 billion. Growing by 13.8 percent, VMT is projected to be 87.5 billion by 2013.

With an estimated fatality rate of 1.12, the expected number of fatalities in 2013 would be 980.4 The goal for 2013 to achieve a fatality rate of 1.0 per 100 million VMT translates into 875 fatalities.5 Therefore, the net reduction in fatalities in 2013 from what is expected to the goal is 105.6 Strategies and efforts that result in 105 fewer fatalities are needed to achieve the goal. Since 20 percent of the fatalities in 2007 occurred in intersection or intersection-related crashes, the intersection component of the overall goal can be estimated as 217 lives saved annually at intersections beginning in 2013.

The economic losses that began in 2008 probably are associated with significant reductions in highway fatalities being realized in 2008. Less travel, particularly less discretionary travel, reduces the risk exposure for a serious crash. Most State SHSP goals are set approximately 5 years out (2012-2013). There is little technical basis to determine the length of the economic downturn. However, one assumption that may be made is that current economic conditions will be gone 5 years from now and should not be taken into consideration. That is, States could use 2007 as the last year of VMT and crash data in the analysis. States may also assume that VMT in 2012 will be equivalent to 2007 and expected fatalities in 2012 would be the mean of those occurring between 2002 and 2007.

Step 1 Action. Create an intersection crash reduction goal that is aligned with and complements the SHSP goal.


1 The expected number of fatalities in 2013 without additional strategies based upon past trends is the number of fatalities in 2007 (1,000) decreased by the results of existing trends and programs in place (1 percent annual decline in fatalities) for 6 years, or 1,000-(1,000 0.01 6) = 1,000-60 = 940.

2 The additional fatality reduction to meet the 2013 goal is the expected number of fatalities in 2013 (940) decreased by the State's 2013 fatality goal (850), or 940-850=90.

3 The expected fatality rate in 2013 is the 2007 rate (1.30) decreased by 3 percent per year for 6 years, or 1.30-(6 x 0.03) = 1.30-0.18 = 1.12.

4 The expected number of fatalities in 2013 is the expected fatality rate in 2013 (1.12 per 100 million VMT) multiplied by the projected VMT (87.5 billion), or (1.12x10-8) (87.5 x 109) = 980.

5 The number of fatalities in 2013 if a 1.0 per 100 million VMT fatality rate is achieved is the fatality rate goal in 2013 (1.0 per 100 million VMT) multiplied by the VMT in 2013 (87.5 billion), or (1.0 10-8) (87.5 x 109) = 875.

6 The net reduction in fatalities in 2013 is the expected number of fatalities in 2013 (980) decreased by the number of fatalities if the 1.0 per 100 million VMT is achieved (875), or 980-875 = 105.

7 The intersection component of the overall goal is the net reduction in fatalities in 2013 (105) multiplied by the percentage of intersection or intersection-related crashes in 2007 (20 percent), or 105 0.20 = 21.

< Previous Table of Contents Next >