Objective Category
System Reliability: Travel Time Buffer Index

Objectives in the area of travel time reliability aim to reduce the variability in travel time so that transportation system users experience a consistent and predictable trip time. Unexpected delay is reduced for people and goods. This category focuses on the buffer time index, which reflects the amount of extra time that travelers need to add to their average travel time to account for non-recurring delay.

Associated Objectives and Performance Measures

Objective	Performance Measure
Decrease the buffer index for (specific travel routes) by X percent over the next Y years.	The buffer index represents the extra time (buffer) most travelers add to their average travel time when planning trips. This is the extra time between the average travel time and near-worst case travel time (95th percentile). The buffer index is stated as a percentage of the average travel time. Average buffer index or buffer time can be calculated using miles traveled as a weighting factor. Buffer time = 95th percentile travel time (min) – average travel time (min).
Decrease the average buffer index for (multiple routes or trips) by X percent over Y years.	The buffer index represents the extra time (buffer) most travelers add to their average travel time when planning trips. This is the extra time between the average travel time and near-worst case travel time (95th percentile). The buffer index is stated as a percentage of the average travel time. Average buffer index or buffer time can be calculated using miles traveled as a weighting factor. Buffer time = 95th percentile travel time (min) – average travel time (min).
Reduce the average buffer time needed to arrive on-time for 95 percent of trips on (specified routes) by X minutes over Y years.	The buffer index represents the extra time (buffer) most travelers add to their average travel time when planning trips. This is the extra time between the average travel time and near-worst case travel time (95th percentile). The buffer index is stated as a percentage of the average travel time. Average buffer index or buffer time can be calculated using miles traveled as a weighting factor. Buffer time = 95th percentile travel time (min) – average travel time (min).

Associated Planning Factors and Goals

Planning Factor	Goal
G. Promote efficient system management and operation;	Improve the efficiency of the surface transportation system
I. Improve the resiliency and reliability of the transportation system and reduce or mitigate stormwater impacts of surface transportation;	Improve the resiliency and reliability of the surface transportation system

Associated Service Packages

Service Package
MC04: Winter Maintenance
MC06: Work Zone Management
TI01: Broadcast Traveler Information
TI02: Personalized Traveler Information
TI03: En-Route Guidance
TI07: In-Vehicle Signage
TM03: Traffic Signal Control
TM04: Connected Vehicle Traffic Signal System
TM05: Traffic Metering
TM06: Traffic Information Dissemination
TM08: Traffic Incident Management System
TM20: Variable Speed Limits
TM21: Speed Harmonization
TM22: Dynamic Lane Management and Shoulder Use
VS05: Curve Speed Warning
VS08: Queue Warning
VS09: Reduced Speed Zone Warning / Lane Closure
VS10: Restricted Lane Warnings

Source

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