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Objectives
• Concept of passing lane analysis
• Comparison of passing and climbing lanes analysis
• Understand application
HCM 2000 Concept of Auxiliary Lane Effects on PTSF
PTSFd Directional PTSF estimate without the auxiliary lane
Lu Length of highway upstream of auxiliary lane (miles)
Lpl Length of passing lane (miles)
Lde Downstream length of highway with PTSF affected by auxiliary lane
Ld Length of highway downstream of auxiliary lane beyond the effect of the auxiliary lane
HCM 2000 Concept of Auxiliary Lane Effects on ATS
ATSd Directional ATS estimate without the auxiliary lane
Lu Length of highway upstream of auxiliary lane (miles)
Lpl Length of passing lane (miles)
Lde Downstream length of highway with ATS affected by auxiliary lane
Ld Length of highway downstream of auxiliary lane beyond the effect of the auxiliary lane
Method of Adjustment• PTSFpl = A2/LT
• A2 = PTSFd * Lt – A1
• A1 = (PTSFd – PTSF * fpl) * (Lpl) + (PTSFd – PTSF * fpl)*(Lde) * ½
PTSFd
PTSFd * fpl
A1
A2
Length
PT
SF
Basic Assumptions
• Directional PTSF and ATS are constant• No relation between passing lane length and
downstream affected length• No affect of adjacent auxiliary lanes• Independent of passing location relative to grade
Overall HCM 2000 Process of Analyzing Auxiliary Lanes
• An auxiliary lane is a second lane added for the benefit of traffic operations…
• Perform directional analysis • Determine location and length of the auxiliary lane• Secure factors
• Calculate adjustments• Adjust ATS and PTSF values
Basic Trends
• As volume rises effectiveness of auxiliary lane ___________
• Effectiveness of a climbing lane is _____________than that of a passing lane
• PTSF is _______sensitive to auxiliary lane effects