Long Description: Figure 1. Example Safety Performance Function

Figure 1 is line graph depicting the type of relationship often found between crash frequency and exposure. Start at 0 for both crashes per unit of time and annual driving miles, the line quickly rises to 3 crashes per unit time at 3000 annual driving miles, where it then begins to level slowing the crashes per unit time to just under 4 at slightly more than 4000 annual miles. The line continues upward at less aggressive pace ending at just above 5 crashes per unit time and 9000 annual miles.

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