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OCR for page 11
11 Motorized vehicle volumes, and Ln = Natural log Motorized vehicle speeds. Wol = Width of outside lane Wl = Width of shoulder or bicycle lane Each of the variables is weighted according to stepwise re- fp = On-street parking effect coefficient (=0.20) gression modeling: A numerical LOS score, generally ranging %OSP = Percent of segment with on-street parking from 0.5 to 6.5, is determined along with the corresponding fb = Buffer area barrier coefficient (=5.37 for trees spaced LOS letter grade. Thus, like the bicycle LOS approach (but 20 feet on center) unlike the automobile approach), pedestrian LOS is deter- Wb = Buffer width (distance between edge of pavement mined based on multiple factors. and sidewalk, feet) In developing the pedestrian LOS Model, the researchers, fsw = Sidewalk presence coefficient (= 6 - 0.3Ws) SCI staff under contract with FDOT, conducted stepwise re- Ws = Width of sidewalk gression analyses using 1,315 real-time observations from a Vol15 = Count of motorized vehicles in the peak 15 minute research effort conducted in 2000 in Pensacola, Florida. period Many of the terms in the pedestrian LOS model equation are L = Total number of directional through lanes also used to determine automobile LOS in the HCM method- SPD = Average running speed of motorized vehicle traffic ology and bicycle LOS in the bicycle LOS model. The logarith- (mi/hr) mic and exponential functions make the importance of the variables differ significantly depending on the precise value. The pedestrian LOS score (PLOS) is estimated according 2.2 Evaluation Against NCHRP 3-70 to the equation below. (This formula differs from the formula Framework Objectives originally produced as part of the Pensacola survey. FDOT has retained the variables from the original survey but the co- This section evaluates the three major guidebooks on level efficients and constant have been changed. See Phillips, of service against the NCHRP 3-70 objectives for a multi- Karachepone, and Landis [9] for original PLOS equation.) modal level of service framework for urban streets. Exhibit 20 The PLOS score is entered in the above table to obtain the summarizes the conclusions. The following paragraphs ex- equivalent LOS letter grade. plain these conclusions in more detail. PLOS = -1.2276 ln (Wol + Wl + fp %OSP + fb Wb + fsw Ws) + 0.0091 (Vol15/L) Highway Capacity Manual + 0.0004 SPD2 + 6.0468 (Eq. 4) Exhibit 21 critiques the LOS criteria used in the Highway Where Capacity Manual. Exhibit 22 critiques the intermodal rela- PLOS = Pedestrian level of service score tionships incorporated in the Highway Capacity Manual. Exhibit 20. Evaluation of Major LOS Manuals Against NCHRP 3-70 Framework Objectives. Framework Objective HCM TCQSM FDOT Q/LOS 1. National Application Designed for Nation Designed for Nation Designed for State 2. LOS is Travelers' Claimed, but no proof A blend of traveler and A blend of HCM, TCQS Perspective operator perspectives and traveler surveys 3. Applicable to Urban Yes Yes Yes Streets 4. Considers All Many factors Many factors Many factors factors within ROW considered, but not all considered, but not all considered, but not all 5. Safety and No No Perceived safety Economic Factors included 6. Comparable Modal Uses speed for auto, Only considers transit Different LOS measures LOS bike, and pedestrian, by mode but not transit 7. Modal Interactions Some but not allSee Some but not allSee Some but not allSee table below. table below. table below. 8. LOS Reflects All Only Through Yes, all bus service on Only Through Movements arterial is counted 9. No Averaging Does not average Considers only single Does not average Across Modes mode 10. Not Limited by HCM Limited by HCM HCM limits not Limited by HCM Limits applicable ROW = Right of Way HCM = Highway Capacity Manual LOS = Level of Service

OCR for page 11
12 Exhibit 21. HCM LOS Criteria for Urban Street. Mode LOS Criterion Comments Auto Mean auto speed for through traffic Applies only to arterials, not collector or local streets Transit Hours of Daily Service, These are the two segment LOS criteria for Reliability availability and comfort/convenience Bicycle Mean speed of bicycle through traffic Applies only if designated bicycle lanes are present Pedestrian Mean speed of pedestrian through traffic Applies only if sidewalk is present National Multimodal Application: The HCM is designed only function of the street. It may be less applicable to collec- to be applied nationally for all four modes (i.e., auto, transit, tors where both through movement and access are important bicycle, and pedestrian). functions of the street. Level of Service from a Traveler's Perspective: The HCM Considers All Factors Within Right of Way: The auto claims to predict LOS from the traveler's perspective, but LOS methodology incorporates all geometric and signal op- there is little evidence to support this claim. The service meas- eration factors considered relevant to the prediction of auto ures were developed in committee without specific research speed. The transit LOS method does not yet have a method- of traveler opinions to support the selected service measures. ology for incorporating the effects of signal operation, traffic Applicable to Urban Streets: The HCM is designed to be flow, and other factors in the right of way that can influence applied to urban arterials where the through movement is the bus service reliability. The pedestrian and bicycle LOS Exhibit 22. The Modal Operational Inter-Relationships in the HCM. Mode Auto Transit Bicycle Pedestrian Auto Higher auto The effect cannot Higher auto For signalized volumes reduce be computed. volumes indirectly intersections, higher auto auto LOS. Higher auto affect bicycle LOS volumes indirectly affect volumes may by affecting delays pedestrian LOS by reduce reliability, at signals. affecting delays at but no estimation signals. For unsignalized method is intersections, higher auto available in the volumes directly affect HCM. Higher auto pedestrian delays and, volumes have no therefore, pedestrian direct effect on LOS. span of transit service. Transit Higher transit The effect cannot Higher transit Higher transit volumes volumes reduce be computed. volumes reduce reduce capacity and capacity and Higher bus capacity and increase delays at increase delays at volumes may increase delays at signalized intersections signalized reduce reliability, signalized intersections but no effect on intersections span of service. Bicycle Higher bicycle The effect cannot Higher bicycle Higher bicycle volumes volumes reduce be computed. volumes reduce have NO effect on walk capacity and Heavy bicycle mean segment speed or delay at signals. increase delays at volumes may speed which signalized reduce reliability, reduces LOS intersections but no impact on (HCM Exhibit 19-3) span of service. Pedestrian Higher pedestrian The effect cannot Pedestrian flows The effect is indirect volumes reduce be computed. between 1 and except at unsignalized capacity and Higher pedestrian 60/hr. may crossings where higher increase delays at flows may affect indirectly affect pedestrian flows affect the signalized reliability but not bicycle LOS by group critical gap and intersections span of service. affecting delays at therefore pedestrian signals. Higher delay. volumes have NO effect. Shaded boxes indicate weak or non-existent inter-relationships. No effect means that a change in modal volume has no effect on LOS as computed per the HCM.