6.0 IDRM TREATMENT RECOMMENDATIONS

When IDRM identifies a potential intersection design concern, it also identifies design changes and other measures that could eliminate or mitigate the concern. These are referred to as "treatments." Treatments that could mitigate each identified concern are presented to the user through the IDRM user interface.

The IDRM knowledge base relates concerns to the applicable treatments by means of the treatment recommendation matrix. A row in this matrix is specified by a concern, a specific geometric condition or other design element related to the concern, and a treatment that addresses that condition. For some treatments, the design element is designated as "general," indicating that the treatment is potentially applicable to the concern, regardless of the specific design element related to the concern.

Each treatment is categorized as either a "design improvement" (generally higher cost) or a "mitigation measure" (generally lower cost).

Table 26 and Table 27 present the IDRM treatment recommendation matrix for intersection concerns and intersection-leg concerns, respectively.

Table 26. List of Treatments (Design Improvements and Mitigation Measures) for Intersection Concerns

Concern Messages	Design Improvements	Mitigation Measures
4.20 Insufficient Left-Turn Bay Storage and Deceleration Length Between Closely Spaced Intersections
- back-to-back left-turn lanes	Relocate one or both minor-road legs Close one minor-road leg Provide an alternative path around the intersection for minor-road vehicles Convert to back-to-back parallel left-turn lanes	Prohibit left turns Restrict left turns Signalize intersection (if unsignalized) Convert to all-way stop Restripe with shorter taper
4.21 Insufficient Taper Length for Left-Turn Lanes Between Closely Spaced Intersections
- back-to-back left-turn lanes	Convert back-to-back to parallel left-turn lanes Relocate one or both minor-road legs Close one minor-road leg Provide an alternative path around the intersection for minor-road vehicles	Prohibit turns Convert to all-way stop (if unsignalized) Restripe with shorter taper

Table 26. List of Treatments (Design Improvements and Mitigation Measures) for Intersection Concerns (continued)

Concern Messages	Design Improvements	Mitigation Measures
4.22 High Traffic Conflict Index
- multileg intersection	Relocate one or more legs Make one or more legs one-way Close one or more legs	Signalize (if unsignalized) Prohibit turns Restrict turns
4.24 Large Intersection Pavement Area
- multileg intersection	Add channelizing islands Relocate one or more legs Close one or more legs Consider smaller design vehicle Improve drainage Consider roundabout	Supplemental dotted line Add painted channelization
- skewed intersection	Realign one or more legs (consider offset T) Add channelizing islands Relocate one or more legs Close one or more legs Consider smaller design vehicle Improve drainage	Supplemental dotted line Add painted channelization
- large vehicle turn path	Realign approach Rechannelize turn to accommodate design vehicle (if channelization present) Increase throat width Remove unnecessary channelization (if channelization present) Consider smaller design vehicle	Move stop bar

Table 27. List of Treatments (Design Improvements and Mitigation Measures) for Intersection-Leg Concerns

Concern Messages	Design Improvements	Mitigation Measures
4.1 - 4.7 Insufficient ISD to right (Case B1) for ___ leg
- general	Remove roadside obstacles within sight triangle Close approach Relocate approach Make leg one-way away from intersection Reduce upgrade on approach (if upgrade is present)	Remove roadside obstacles within sight triangle Signalize intersection (if unsignalized) Convert to all-way stop (if unsignalized) Convert yield control to stop control (if yield- controlled) Post advisory speed on major road Review speed limit on major road Install warning sign on major road Install flashing beacons (if unsignalized) Prohibit left turn Provide intersection lighting
- multileg intersection	Close one or more legs Relocate one or more legs
- skewed intersection	Realign one or more legs Relocate one or more legs Close one or more legs
- more than one minor-road approach on the same side of the major road	Close one or more legs Relocate one or more legs Make one or more legs one-way
- horizontal curve	Increase curve radius Remove roadside obstacles on inside of curve
- crest vertical curve	Lengthen vertical curve