The 2010 and 2016 Highway Capacity Manual Signalized Intersection Methodology

Abstract

The 2010 HCM (Highway Capacity Manua in Special report 209, Transportation Research Board, Washington D.C., [1]) signalized intersection methodology completely changed the organization and emphasis of the chapter on isolated signalized intersections. Previous versions of the signalized intersection chapter presented a pretimed methodology, with an appendix added in 1997 containing an outline for determining an average cycle length and phase times for an actuated controller. The 2010 and 2016 HCMs are organized to present the methodology for an actuated signal, with pretimed signal phasing handled as a subset of the actuated controller methodology by setting all the recall settings to maximum.

Appendix

• Maximum Allowable Headway Equations for All Lane Group Types

The general equation for MAH for presence detectors, shown earlier in Eq. 9.50, needs to be modified for the various possible lane group types to account for differences in vehicle behavior of turning vehicles. The base Eq. 9.50 is rewritten here as Eq. 9.75 for through vehicles.

$$ MAH_{th} = PT_{th} + \frac{{L_{ds,th} + L_{v} }}{{1.47S_{a} }} $$

(9.75)

where:

PT_th:

passage Time for phase serving through vehicles

L_ds:

length of the stop-line detection zone in the through lanes.

The following equations are used to calculate the MAH for all other lane group types.

For protected left turns from an exclusive left-turn lane (or protected-permitted), use Eq. 9.76

$$ MAH_{lt,prot,e} = PT_{lt} + \frac{{L_{ds,lt} + L_{v} }}{{1.47S_{a} }} + \frac{{E_{L} - 1}}{{s_{o} /3600}} $$

(9.76)

where:

E_L:

left-turn equivalent for a protected left-turn = 1.05

s_o:

base saturation flow rate (pc/h/ln).

For left turns made from a shared lane with protected-permitted phasing, use Eq. 9.77

$$ MAH_{lt,prot,s} = MAH_{th} + \frac{{E_{L} - 1}}{{s_{o} /3600}} $$

(9.77)

For permitted left turns from a exclusive lane use Eq. 9.78

$$ MAH_{lt,perm, e} = PT_{th} + \frac{{L_{ds,lt} + L_{v} }}{{1.47S_{a} }} + \frac{3600}{{s_{l} }} - t_{fh} $$

(9.78)

where:

t_fh:

follow-up headway (4.5 if left turn is made from a shared lane and 2.5 if left turn is made from an exclusive lane).

For permitted left turns in a shared lane, use Eq. 9.79:

$$ MAH_{lt,perm, s} = MAH_{th} + \frac{3,600}{{s_{l} }} - t_{fh} $$

(9.79)

For protected right turns from an exclusive right-turn lane, use Eq. 9.80:

$$ MAH_{rt,p,e} = PT_{rt} + \frac{{L_{ds,rt} + L_{v} }}{{1.47S_{a} }} + \frac{{E_{R} - 1}}{{s_{o} /3600}} $$

(9.80)

where:

E_R:

protected right-turn equivalent = 1.18.

For permitted right turns made from an exclusive right-turn lane, use Eq. 9.81:

$$ MAH_{rt,perm,e} = PT_{th} + \frac{{L_{ds,rt} + L_{v} }}{{1.47S_{a} }} + \frac{{\left( {E_{R} /f_{Rpb} } \right) - 1}}{{s_{o} /3600}} $$

(9.81)

where:

f_Rpb:

pedestrian-bicycle saturation flow rate adjustment factor.

For permitted right turns made from a shared lane, use Eq. 9.82:

$$ MAH_{rt,perm,s} = MAH_{th} + \frac{{\left( {E_{R} /f_{Rpb} } \right) - 1}}{{s_{o} /3600}} $$

(9.82)