CE 578 Highway Traffic Operations

Passing Lanes and Climbing Lanes HCM 2000

Objectives

• Concept of passing lane analysis

• Comparison of passing and climbing lanes analysis

• Understand application

PTSF Trends with and without a Passing Lane

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

Equation for PTSFd Adjustment

Equation for ATSd Adjustment

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

Tables for Lde and fpl: Passing and Climbing Lane

Tables for Lde and fpl: Passing and Climbing Lane

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

Application to Passing LanesGiven:PTSFd = 80 ATSd = 45 mphLt = 10 miles Lu = 2 miles Lpl = 1 milevp_PTSF = vp_ATS = 700 pc/hr

use Equations 20-20 and 20-22 for situations where Lt < Lu + Lpl + Lde