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Calculating Multi-Modal
Levels-Of-Service (abridged)

 

 

 


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by David Mozer

Pedestrian  |  Bicycle  |  Transit / Buses

Introduction

The proficiency of roads are described by their 'Level Of Service' (LOS). The criteria are defined in the Highway Capacity Manual (HCM). Current LOS's (A to E) reflect only the ability of roads to accommodate motor vehicle traffic, where 'A' is free- flowing and 'E' is heavily congested. This traditional analysis does nothing to measure or preserve levels of access for pedestrians, bicycles or transit. To reflect the value of pedestrians, bicyclists and transit the evaluation of 'level of service' needs to be revised. Work is now being done by engineers in Europe, America and Australia to revise the HCM. It is critical for advocates of alternative transportation to be involved for meaningful revisions to be adopted.

This paper proposes a methods for determining the LOS for pedestrians, bicycles and transit. Together with the traditional LOS you arrive at a Pedestrian, Bicycle, Auto, Transit Level of Access (P-BAT LOA). Transportation systems wishing to encourage alternatives to the single occupancy vehicle should try to raise pedestrians, bicycle and transit LOSs up to or above the traditional LOS. For example: A pedestrian-friendly 'old town' type shopping area might aim for a P-BAT LOA of 'BCCB'.

A practical criteria of LOS for pedestrians and bicyclists is:

  • A - Facility is reasonably safe for all users 10 years or older. It may also be safe for solo users as young as 6 years old.  But, in some Level A areas some children under 10 may still need to be supervised.
  • B - Facility can accommodate users with basic skills and knowledge of traffic.
  • C - Facility requires an intermediate level of skill and knowledge of traffic to use.
  • D - Facility requires an advanced level of skill and knowledge of traffic to use.
  • E - Facility is generally not suitable for pedestrians or bicyclists. Note: Each modes LOS is determined separately and by using criteria specific to that mode. The criteria doesn't try to quantify every possible factor, just the most pivotal characteristics. For each variable a 'stress level' (SL) is measured and set on a scale of one to five. The high the SL the lower the level of service. These are added and then an averaged to determine the LOS. This is an approximation of how user perceives the level of service while using the street. Evaluations are made mid-block on a discrete segment of the facility. Consecutive blocks can have different LOS.

LOS Pedestrians

Determining the suitability of street segments for pedestrians, is based on four primary variables; walkarea width-volume, walkarea-outside lane buffer, outside lane traffic volume, outside lane motor vehicle speed, plus three secondary factors; walkarea penetrations, heavy vehicle volumes and intersection wait-time. These are examined in more detail below:

Walkarea Width-Volume

This is the most important variable for pedestrians because it measures their secure operating space. Where areas used by pedestrians are not grade separated, their space would be the useable area outside the lane edge stripe. Linear space taken up by 'street furniture' at any point in the segment should not be included. Peak hour volumes are used. Because this is the primary factor it is given a double weight (2X) in the calculations. The walkarea width-volume is determined by the following relationship:

WALKAREA WIDTH-VOLUME (wwv) = PHV x (1 + NPM) / (WWA / (TP x FD))
PHV = Peak hour pedestrian volume, all directions.
NPM = Mode split that is none pedestrians (for example: wheelchairs, bicyclists, skaters, bladders,runners).
WWA = Width of the walkarea, in meters.
TP = Travel Pattern Factor; if predominately oneway enter '1', if predominately bi-directional enter'2'.
FD = Facility Design Factor; if facility meets Americans with Disabilities Act requirements (steps,slope, side slope) enter '1', if facility does not meet Americans with Disabilities Act requirements enter '5'.

The SL for walkarea width-volume are:

SL Walkarea Width-Volume

  1. 100
  2. 200
  3. 300
  4. 400
  5. >500

Walkarea-Outside Lane Buffer Factor

Buffer space between motor vehicle traffic and pedestrians increases the safety and aesthetic experience of pedestrians. Ideally the buffer is a planted strip, but a lane of on-street parking, an area of 'street furniture' or a jersey barrier also improves conditions for pedestrians. The SL for walkway-outside lane buffers is determined by the following relationship:

WALKAREA-OUTSIDE LANE BUFFER FACTOR (lbf) = WBW / EQ
WBW = Walkarea-Outside Lane Buffer Width
EQ = Aesthetic Quality, if living material enter '1', if non-living material enter '2'.
The SL for walkarea-outside lane buffers are:

SL Walkway-Outside Lane Buffer Factor

  1. >1.7 meters/>5 feet
  2. 1.3/4
  3. 1.0/3
  4. 0.6/2
  5. <0.3/<1

Outside Lane Volume

Outside lane volumes are calculated using peak hour volumes. If the peak hour volume is not known standard procedure is to multiple the average daily total by a constant. On multi-lane roads the volume for one lane volumes is found by dividing the total peak hour volume by the number of through lanes on the street segment. This assumes a 50/50 split on two way streets. If the split is different, then use the known split for analysis. The peak hour volume per lane is determined by the following relationship:

PEAK HOUR VOLUME PER LANE (vpl) = ADT x K (factor) / LN
ADT = Average Daily Traffic
K = Factor that determines the portion of ADT which occurs during the peak hour. K = 10% for urban areas.
LN = Number of lanes.
The SL for volume in the outside lane is determined by the following relationship: vpl / 25 = SL(SL + 1) where SL <5. Sample values are:

SL Outside Lane Volume

  1. <50 vehicles/hr./lane
  2. 150
  3. 300
  4. 500
  5. >750

Outside Lane Speed

The speed of motor vehicles adjacent to the walkarea for pedestrians affects the experience. Speed is measured for the 85% of traffic. The SL for outside lane speed are:

SL Speed of Motor Vehicles

  1. <16 kph/ <10 mph
  2. 32/20
  3. 48/30
  4. 64/40
  5. >80/>50

Walkarea Penetrations Factor

Walkarea penetrations create turning movements which are potentially dangerous to pedestrians. This factor is added to the primary level of stress subtotal. The peak hour walkarea penetration SLs are determined by the following relationship:

PEAK HOUR OUTSIDE PENETRATIONS FACTOR (php) = N x APHP x (1000 / D) / 100
N = Number of Driveways
APHP = Average Peak Hour Penetrations per driveway
D = Distance of the segment in meters. This is a multiplier that gives the number of driveways in a kilometer (.6 miles)

Heavy Vehicle Factor

Because heavy vehicles are often loud and create turbulence their presence is factored into the analysis of the level of stress for pedestrians. This factor is added to the primary level of stress subtotal. The heavy vehicle factor (hvf) SL is determined by the percentage of heavy vehicles using the segment. The figure is added to the primary level of stress as a decimal.

Intersection Wait-time Factor

The wait time to safely cross at an intersection partially reflects on convenience, but also reflects on safety and risk. This factor is added to the primary level of stress subtotal. The wait-time factor (wtf) is determined by the percent of a minute that the pedestrian must wait to cross the street. If the intersection has a fixed phase signal 50% of the 'wait phase' is used. If there is a demand actuated 'walk signal', the time between requesting the right-of-way and receiving the signal is used. If the intersection is non-signalized the average wait for an opening in traffic during the peak hour is used. The figure is added to the primary level of stress as a decimal.

LOS Bicycles

Determining the suitability of street segments for bicycle use, is based on three primary on-street conditions; outside lane width, motor vehicle speeds and traffic volume, plus three additional secondary factors; the quantity of bicycle traffic, volume of heavy vehicle traffic and outside lane penetrations. The level of service is determined by calculating the 'stress level' (SL) for each primary variable, averaging the weighted results and adding the appropriate correction factor of the secondary influences. This gives an approximation of how bicyclists perceive the level of service while riding on a given section of a street.

Outside Lane Width

This variable is critical because it delimits the bicyclist's operating space. Where striped bicycle lanes are present, the sum of the bike lane and adjacent vehicle lane are used. The gutter pan is not included in the analysis. On streets with just a center strip, two travel lanes and on-street parking, subtract three meters or nine feet to account for the parking. Because this is the primary factor it is given a double weight (2X) in the calculations. The SL for outside lane widths are:

SL Outside Lane Width

  1. >4.6 meters/>15 feet
  2. 4.3/14
  3. 4.0/13
  4. 3.7/12
  5. <3.3/<11

Outside Lane Volume

Outside lane volumes are calculated using peak hour volumes. If the peak hour volume is not known standard procedure is to multiply the average daily total by a constant. On multi-lane roads the volume for one lane volumes is found by dividing the total peak hour volume by the number of through lanes on the street segment. This assumes a 50/50 split on two way streets. If the split is different, then use the known split for analysis. The peak hour volume per lane is determined by the following relationship:

PEAK HOUR VOLUME PER LANE (vpl) = ADT x K (factor) / LN
ADT = Average Daily Traffic
K = Factor that determines the portion of ADT which occurs during the peak hour. K = 10% for urban areas.
LN = Number of lanes.

The SL for volume in the outside lane is determined by the following relationship: vpl / 25 = SL(SL + 1) where SL <5. Sample values are:

SL Outside Lane Volume

  1. <50 vehicles/hr./lane
  2. 150
  3. 300
  4. 500
  5. >750

Outside Lane Speed

The speed of motor vehicles in the outside lane also affects a bicyclist's experience. Speed is measured for 85% of traffic. The SL for outside lane speed are:

SL Speed of Motor Vehicles

  1. <16 kph/<10 mph
  2. 32/20
  3. 48/30
  4. 64/40
  5. >80/>50

Width-Bicycle Volume Factor

The width-bicycle volume factor is most significant on heavily used facilities. Peak hour volumes are used. This factor is added to the primary level of stress subtotal. The width-bicycle volume factor is determined by the following relationship:

WIDTH-BICYCLE VOLUME FACTOR (wvf) = PHV x (1 + NBM) x (5 / LW) / 1000
PHV = Peak hour non-motorized volume in "lane", all directions.
NBM = Mode split that is not bicycles (for example: wheelchairs, pedestrians, skaters, bladders,runners).
LW = Width of the outside lane, in meters. Where striped bicycle lanes are present, the sum of the bike lane and adjacent vehicle lane are used. The gutter pan is not included in the analysis

Outside Lane Penetrations Factor

Outside lane penetrations create turning movements which are potentially dangerous to bicyclists. This factor is added to the primary level of stress subtotal. The peak hour outside lane penetrations SLs are determined by the following relationship

PEAK HOUR OUTSIDE LANE PENETRATIONS FACTOR (php) = N x APHP x (1000 / D) / 100
N = Number of Driveways
APHP = Average Peak Hour Penetrations per driveway
D = Distance of the segment in meters. This is a multiplier that gives the number of driveways in a kilometer (.6 miles).

Heavy Vehicle Factor

As heavy vehicles are often wide and create turbulence their presence is factored into the analysis of the level of stress for bicyclists. This factor is added to the primary level of stress subtotal. The heavy vehicle factor (hvf) SL is determined by the percentage of heavy vehicles using the segment. The figure is added to the primary level of stress as a decimal.

On-Street Parking Factor

On-street parking, especially when there is high turnover, increases the risk to bicyclists, from car doors opening and backing movements. This factor is added to the primary level of stress subtotal. The on-street parking factor is determined by the following relationship:

ON-STREET PARKING FACTOR (pf) = ((60 - APT) / 60) x CU
APT = Average parking time in minutes during peak hour
CU = Capacity Utilization during peak hour

LOS Transit / Buses

Much of the effectiveness of transit is determined by the speed, relative to alternatives, at which it can complete its route. Three crucial factors in this are traffic delays, on-time operation and capacity utilization.

Traffic Delay

Much of the running time of transit can be spent sitting at signals. If signal phases are present the average delay is half the time of the red phase (assume the signal clears on each cycle, otherwise the time of a whole cycle must be added in.) If the signal is demand activated by transit the delay is any wait- time generally encountered at the signal.

The SL for traffic delays are:

SL seconds of delay

  1. <5
  2. 15
  3. 25
  4. 35
  5. >45

On time operations

The lack of predictability is often cited as a reason for not using transit. While this can be adjusted in the published schedule, if the elapsed time becomes too long potential users will use other modes of travel.

The SL for on time operations are:

SL minutes late

  1. 0
  2. 2
  3. 4
  4. 6
  5. 8

Capacity Utilization

Standing passengers both increase the off-load/on-load time and discourage potential clients from using transit.

The SL for capacity utilization are:

SL percentage of seat occupied at peak hours

  1. <80
  2. 100
  3. 120
  4. 140
  5. >160

Form 1: Pedestrian Facility Level Of Service Worksheet

omitted *

Form 2: Bicycle Facility Level Of Service Worksheet

omitted *

Form 3: Transit Facility Level Of Service Worksheet

omitted *

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* Unabridged Version: For a copy of the unabridged report, including Level of Service Worksheets write to IBF -- suggested donation of at least US$5 is requested to help support the project. 

Britain now has an official system (or at least quasi official) for rating roads, and other facilities, for cycling.  It comes in a document "Guidelines for Cycle Audit and Review" issued by the Institution of Highways and Transportation, London.   The rating form can be viewed at : http://www.jfparker.demon.co.uk/CRP2.txt (from Jeremy Parker, Oct 1998)

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