TREC Webinar22 April, 2015
Impacts of Roadway and Traffic Characteristics on Air Pollution Risks for Bicyclists
Alex BigazziMiguel FigliozziJim PankowWentai Luo
Health Effects of Bicycling
• Health impact studies for walking & biking have shown that physical activity benefits outweigh crash & air pollution risks by an order of magnitude or more
• Still, we can & should reduce pollution risks
2Urban Bicyclists' Pollution Uptake
Framework
3
Vehicle Emissions
Air Quality
Traveler ExposureInhalation
Uptake Health Effects
Bicyclists' Pollution Uptake
Outline
1. Exposure concentrations
2. Ventilation & inhalation dose
3. Pollutant uptake
4. Applications for transportation planning and design
4Bicyclists' Pollution Uptake
Bicyclists’ Exposures
6
0 5 10 15 20
Ultrafine PM
Fine PM
Coarse PM
Black Carbon
CO
VOC
NO2
# studies measuring on-road bicyclists’ exposure concentrations
Pollutant 42 studies
Bicyclists' Pollution Uptake
9k – 94k pt/cc
0.5 – 13 ppm
5 – 88 µg/m3
Modal Comparisons of Exposure
– Is this actionable information?
Context-dependent results– Bicyclists lower if separated
7Bicyclists' Pollution Uptake
vsvs
High-Traffic/Low-Traffic Routes
8Bicyclists' Pollution Uptake
-50%
0%
50%
100%
150%
200%
250%
CO VOC UFP PM2.5 PM10 BC
Expo
sure
Inc
reas
e on
H
igh-
Traf
fic R
oute
s
N=6 N=11 N=8 N=6 N=3 N=5
PSU Bike Exposure Research
9Urban Bicyclists' Pollution Uptake
How can we reduce exposure risks for bicyclists?
Results: VOC Exposure Models
• +2% per 1,000 ADT
• +20-30% in stop-and-go riding
• Off-street path +300% in industrial
corridor
12Bicyclists' Pollution Uptake
13
Parallel Path Comparison
Bicyclists' Pollution Uptake
E Burnside St. SE Ankeney St.
N Williams Ave. NE Rodney Ave.
Naito Pkwy. Riverside Path
Ventilation and Exercise
15Bicyclists' Pollution Uptake
50 100 150 200 250 Watts
Vent
ilatio
n (
liter
/min
) 75
50
25
Ventilation is strongly related to exertion level
Ventilation & Bicycle Studies
16
57 studies assessbicyclists’ exposure
Ignored38
Constant16
Assumed/Modeled
15Measured
1
Variable3
Modeled 2
Measured1
Ven
tila
tio
n:
Urban Bicyclists' Pollution Uptake
Bicyclist Ventilation
17Urban Bicyclists' Pollution Uptake
0
1
2
3
4
5
0 5 10 15 20Ratio
of
Bic
ycle
/Mot
oriz
ed
Trav
eler
Ven
tilat
ion
Bicycle Speed (mph)
AllMenWomen
Modal Comparisons of Dose
18Urban Bicyclists' Pollution Uptake
-100%
-80%
-60%
-40%
-20%
0%
20%
40%
60%
Pedestrian Car/Taxi Bus
Dif
fere
nce
fro
m B
icyc
list
Dos
e
COUFPPM2.5
N
(3)
(3)
(5)
PSU Research Findings
• 4-8% increase in ventilation per 10 W
• Mean lag ~50 sec
• Highly variableon-road
19Bicyclists' Pollution Uptake
0 50 100 150
0.0
0.2
0.4
0.6
0.8
Seconds workload lagged
Cum
ulat
ive im
pact
on ve
ntila
tion
(%
SubjecABCPooled
% Δ
vent
ilatio
n pe
r W
Seconds lag
Bicyclist Uptake Studies
2 studies of biomarkers:
• VOC: blood & urine– Urban bikers > rural bikers
• BC: induced sputum– Bicyclists > transit riders
21Bicyclists' Pollution Uptake
Breath BiomarkersExhaled breath is a good proxy for
blood concentrations of VOC
22Bicyclists' Pollution Uptake
alphaszenszor.com
VOC in blood
1) Local roads
Pre Breath
Post Breath
PSU On-Road Sampling
20-30 minutes, 3-5 milesExposure & breath VOC
Paired subjects
23Bicyclists' Pollution Uptake
Pre Breath
Post Breath
2) Major arterials
Breath and Exposure Concentrations
0 1 2 3
Breath
Exposure
Concentration (normalized to Park)
Toluene
Major arterials
Local streets
24Bicyclists' Pollution Uptake
Breath Sampling Results
• The breath sampling method works– Exposure predicts breath concentrations– Δ Breath ~ ½ Δ Exposure
• 10-60% higher on major arterials than local streets– Traffic impact (over BG) 3-5x greater on
major arterials than local streets
25Urban Bicyclists' Pollution Uptake
Explained variance in breath BTEX
26Bicyclists' Pollution Uptake
0%
10%
20%
30%
40%
50%
Measured variables Modeled variables
Exposure
Ventilation
Exposure variability
Weather variables
Road & traffic
variables
Exercise and Uptake
• Ventilation/inhalation rate: 2-5x higher
• PM uptake: ≥2-5x higher
• VOC uptake: 1.5-2x higher
27Bicyclists' Pollution Uptake
Route Choice
• Detour to reduce inhalation dose if:– <46% longer than minor arterial route– <123% longer than major arterial route
• Inhalation doses +20-30% per 1% grade
29Bicyclists' Pollution Uptake
?
Comparison with Preferences
30Bicyclists' Pollution Uptake
Will bicyclists naturally minimize inhaled dose over a trip?
Bike boulevard
or
neighborhood greenway
Bike lane
Minor arterial (no bike lane)
Major arterial (no bike lane)
• Slightly over-avoid
• Balance on collectors (6-10k ADT) • Under-avoid arterials
• Greatly over-avoid
vs.
vs.
vs.
Inhalation and Stops
31Urban Bicyclists' Pollution Uptake
0
100
200
300
400
500
600
6 8 10 12 14 16 18
Cru
ise-
equ
ival
ent
exce
ss
ven
tila
tio
n (
ft)
Cruise speed (mph)
Inhalation and Speed
32Bicyclists' Pollution Uptake
0
50
100
150
200
250
300
0 4 8 12 16
Ven
tila
tion
(l/
km)
Speed (mph)
0% Grade2% Grade
Bikeway Design ConsiderationsBike lane • Higher-traffic streets
• Some lateral separation• Dedicated lane reduces stops in
congestion
Cycle track • Higher-traffic streets• More lateral separation
Bike boulevard
• Low-traffic streets• Additional benefits from traffic calming• Fewer stops reduces doses
Off-street path
• Low exposure (nearby industry?)• Fewer stops reduces doses
33Bicyclists' Pollution Uptake
Take-Away Principles
1. Bicyclist Exposure a) Many different pollutantsb) Traffic, weather, and land-use all important c) Benefits of separation from traffic
2. Bicyclist Inhalationa) Varies greatly with workload (speed, grade)b) Breath response spread out over 1-2 min
3. Bicyclist Uptakea) For particles, highly sensitive to breathingb) For some gases, more sensitive to exposure &
duration
34Bicyclists' Pollution Uptake
Future Work
• Abstraction for HIA & CBA• Characterizations of urban bicyclists • Similar study for pedestrians• Crowd-source pollution data
35Bicyclists' Pollution Uptake
Questions?
36Bicyclists' Pollution Uptake
Acknowledgments• Miguel Figliozzi, Jim Pankow, Wentai Luo• NITC, City of Portland, Portland Metro, NSF, OTREC
Steady-state biking work
38Bicyclists' Pollution Uptake
0
50
100
150
200
250
0 2 3 5 6 8 9 11 13 14 16
Wor
kloa
d (W
)
Speed (mph)
Rolling Resistance Drag 1% Grade