In Alternative Design, the Adjustment Factor may be presented as a weighted value for site characteristics listed below. This approach allows users to understand the overall impact of a proposed change on the facility, rather than viewing separate Adjustment Factors for each crash type and severity.
When multiple crash predictions are present and vary by crash type and severity, Alternative Design calculates a weighted average Adjustment Factor. Although the Adjustment Factor for individual crash types and severities may be higher, the weighted value accounts for all crash types/severities and displays a single representative value.
Weighted adjustment factor equation used in the Alternative Design application:
The following adjustment factors for the specified roadway or intersection type will have the weighted Adjustment Factor (using the equation above) displayed in-app:
Segments
Freeway Segment (ISAT-e)
Adjustment Factor | Crash Type | Severity |
Inside Shoulder | All | FI, PDO |
Median Width | MV, SV | FI, PDO |
Lane Width | MV, SV | FI |
Horizontal Curve | MV, SV | FI, PDO |
Outside Shoulder Width | SV | FI, PDO |
Shoulder Rumblestrips | SV | FI |
Outside Barrier | SV | FI, PDO |
Outside Clearance | SV | FI |
High Volume | MV, SV | FI, PDO |
Median Barrier | All | FI, PDO |
Lane Change | MV | FI, PDO |
Speed Change Lanes
(Note: users must add a speed change lane as a related segment in the project selection page)
Adjustment Factor | Crash Type | Severity |
Horizontal Curves | All | FI, PDO |
Lane Width | All | FI |
Inside Shoulder Width | All | FI, PDO |
Median Width | All | FI, PDO |
Median Barrier | All | FI, PDO |
High Volume | All | FI, PDO |
Ramp Entrance/Exit | All | FI, PDO |
Ramp Segments and Collector/Distributor (CD) Segment
Adjustment Factor | Crash Type | Severity |
Lane Width | MV, SV | FI |
Right Shoulder Width | All | FI, PDO |
Left Shoulder Width | All | FI, PDO |
Right Side Barrier | All | FI, PDO |
Left Side Barrier | All | FI, PDO |
Weaving (CD-Segment Only) | All | FI, PDO |
Lane Add / Drop | MV, SV | FI |
Ramp Speed Change Lane | MV | FI |
Horizontal Curves | MV, SV | FI, PDO |
Intersections
Ramp Terminal (ISAT-e)
Adjustment Factor | Traffic Control | Crash Type | Severity |
Exit Ramp Capacity | Ramp Stop Controlled | All | FI |
Exit Ramp Capacity | Signalized | All | FI |
Channelized Right-Turn Lane on Crossroad | Signalized | All | FI, PDO |
Crossroad Left Turn Lane | All | All | FI, PDO |
Crossroad Right Turn Lane | All | All | FI, PDO |
Access Point Frequency | Ramp Stop Controlled | All | FI |
Access Point Frequency | Signalized | All | FI, PDO |
Segment Length to Adjacent Intersection | Ramp Stop Controlled | All | FI |
Segment Length to Adjacent Intersection | Signalized | All | FI, PDO |
Protected Left-Turn Lane Operation | Signalized | All | FI, PDO |
Channelized Right-Turn Lane on Exit Ramp | Signalized | All | FI, PDO |
Non-Public Street Leg | Signalized | All | FI, PDO |
Skew Angle | Ramp Stop Controlled | All | FI |
Median Width | Ramp Stop Controlled | All | FI |
Median Width | Signalized | All | FI, PDO |