Signalized Intersections LOS. Signalized Intersection Analysis and Level of Service. Signalized Intersections LOS. Lane Grouping 11/17/2009

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1 Sgnalze Intersecton nalyss an Leel of Serce CE3 Transportaton Engneerng Dr. hme bel-rahm Sgnalze Intersectons LOS Recall that leel of serce (LOS) s a qualtate assessment of faclty operatons base upon a quanttate performance measure. The performance measure that s use to assess leel of serce for sgnalze ntersectons s aerage control elay per ehcle. Sgnalze Intersectons LOS nalyss Proceure (assumng phasng, cycle length, an effecte green tmes hae alreay been etermne) Establsh nalyss Lane Groups Calculate nalyss Flow Rates an juste Saturaton Flow Rates Calculate Capactes Calculate Delay Determne Leel of Serce (LOS) Lane Groupng The methoology for sgnalze ntersectons s saggregate; that s, t s esgne to conser nual ntersecton approaches an nual lane groups wthn approaches. Segmentng the ntersecton nto lane groups s a relately smple process that consers both the geometry of the ntersecton an the strbuton of traffc moements. In general, the smallest number of lane groups s use that aequately escrbes the operaton of the ntersecton.

2 Lane Groupng Lane groups wll generally be ctate by geometry (.e., lane allocaton) an phasng Sgnalze ntersecton phasng can range from smple to complex Pretme sngle rng Fully actuate ual rng Lane Groupng Dual-rng Sgnal Control Calculate nalyss Flow Rates just hourly olumes for RTOR just for peak hour factor (PHF) ssume alreay accounte for n book problems

3 Calculate juste Saturaton Flow Rates Start wth a base alue, usually 900 pc/hr/ln per the Hghway Capacty Manual Ths alue s then ajuste for a arety of roaway an traffc relate contons. Factors such as lane wth, grae, heay ehcle percentage, bus actty, parkng actty, peestran an bcyclst actty, an turn moement geometry an phasng Calculate Lane Group Capactes Capacty s etermne on a lane group bass c = s g/c s = ajuste saturaton flow rate g/c = eff. green to cycle length rato Determnng Delay erage control elay per ehcle PF Eq = aerage sgnal elay per ehcle n secons, = aerage elay per ehcle ue to unform arrals n secons, PF = progresson ajustment factor, = aerage elay per ehcle ue to ranom arrals n secons, an 3 = aerage elay per ehcle ue to ntal queue at start of analyss tme pero, n secons. Determnng Delay Unform elay g 0.5C C g mn, X C Eq. 7.5 = aerage elay per ehcle ue to unform arrals n secons, C = cycle length n secons, g = effecte green tme for lane group n secons, an X = /c rato for lane group. 3

4 Determnng Delay Ranom elay 8kIX X X 900T Eq. 7.6 ct = aerage elay per ehcle ue to ranom arrals n secons, T = uraton of analyss pero n h, X = /c rato for lane group, k = elay ajustment factor that s epenent on sgnal controller moe, I = upstream flterng/meterng ajustment factor, an c = lane group capacty, n eh/h. Delay Calculaton ssumptons For problems n ths class, all ntersectons are assume to be solate, uner pretme control, an hae no ntal queue at begnnng of analyss pero; thus: 3 0 PF.0 k 0.5 I.0 Determnng Delay ggregatng Delays = aerage elay per ehcle for approach n secons, = aerage elay per ehcle for lane group (on approach ) n secons, an = analyss flow rate for lane group n eh/h. I I = aerage elay per ehcle for the ntersecton n secons, = aerage elay per ehcle for approach n secons, an = analyss flow rate for approach n eh/h. Eq. 7.7 Eq. 7.8 Leel of Serce Delay Threshols LOS Control Delay per Vehcle (s/eh) 0 B > 0-0 C > 0 35 D > E > F > 80 4

5 Example Phasng Traffc Volumes & Lanes 3 nalyss Flow Rates an j. Sat. Flow Rates juste nalyss Flow Rates Use gen olumes juste Saturaton Flow Rates Phase (E/W prot. LT s): 800 eh/h Phase (E/W Th/RT s): 3450, 3500 eh/h Phase 3 (N/S perm. LT s): 500, 350 eh/h (N/S Th/RT s): 800 eh/h Calculate Flow Ratos (/s) an Ientfy Crtcal Ones Phase Phase Phase EB L: 0. EB T/R: NB L: WB L: WB T/R: 950 SB L: NB T/R: SB T/R:

6 Determne Cycle Length n Yc s c ssumng 4 secons of lost tme per phase L n t L c ssumng a crtcal ntersecton /c rato of 0.8 C mn L X c 0.8 = n X c = s c Determne Effecte Green Tmes for each Phase g s C X 00 g g g C = = 00. Calculate EB approach elay Left turn lane group g/c = 7.4/00 = 0.74 (moes n phase ) c = s g/c = = 33. /c = 0/33. = 0.70 Unform Delay sec Ranom Delay Wth: T = 0.5 (5 mn) X = 0.70 (from aboe) k = 0.5 (pretme control) I =.0 (solate moe) c = 33. eh/h (from aboe) sec 0.5 6

7 LT Total Delay Wth PF =.0 (for solate sgnal) sec Calculate EB approach elay Through/Rght turn lane group g/c = 33.9/00 = (moes n phase ) c = s g/c = = 69.6 /c = 880/69.6 = 0.75 Unform Delay sec Ranom Delay Wth: T = 0.5 (5 mn) X = 0.75 (from aboe) k = 0.5 (pretme control) I =.0 (solate moe) c = 69.6 eh/h (from aboe) Total Delay Wth PF =.0 (for solate sgnal) T / R sec sec 0.5 7

8 ggregate elays for LT an T/R lane groups EB LT LT LT T / R T / R T / R EB sec