dynamic ride-sharing systems: a case study in metro atlanta niels agatz joint work with alan erera,...
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Dynamic Ride-sharing Systems: a Case Study in Metro Atlanta
Niels Agatz
Joint work withAlan Erera, Martin Savelsbergh, Xing Wang
ARCFebruary 26, Atlanta
Motivation
ObservationsCongestion is a major issue in urban areas
around the worldCongestion leads to
• Loss of productivity• Wasted fuel• Pollution
Private car occupancies are low• Average of 1.8 for leisure trips• Average of 1.1 for commuting trips
Motivation
OpportunityEffective use of empty car seats can
• Reduce congestion• Reduce fuel consumption• Reduce pollution• Increase productivity
Enabling technology exists• GPS-enabled mobile devices• Mobile-to-mobile communication• Route guidance technology
Dynamic Ride-Sharing
Outline
Introduction to dynamic ride-sharing A dynamic ride-share setting Solving the problem Simulation Metro Atlanta Simulation Results
1. Announcement of trips
2. Matching of drivers and riders
3. Execution of identified trips
4. Sharing of trip costs
Dynamic ride-sharing: basics
Assumption: if no trip is identified, drivers and riders
use their own car to reach destination
Dynamic ride-sharing: features
Dynamic: established on short-notice Non-recurring trips: different from carpooling Automated matching: different from online notice-
boards Independent drivers: different from taxis Cost-sharing: variable trip related expenses Prearranged: different from spontaneous, casual
ride-sharing
Dynamic ride-sharing: providers
IPhone applications: Carticipate (Aug. ‘08) Avego (Dec. ‘08)
Google Android applications: Piggyback (May ‘08)
Web-based: Zebigo, PickupPal, Nuride, Rideshark, Ridecell,
Goloco, Zimride, …, etc.
What is in it for participants?
Save costs by sharing fuel expenses and tolls Save time through use of HOV-lanes Save the planet
What is in it for providers?
Private: take a cut of the participant’s cost savings
Public (society): decrease external costs of transportation: emissions, pollution, and traffic congestion
Objectives
Participants: ↓ travel costs Private ride-share provider: ↓ total travel costs
↑ cut Society: ↓ pollution and traffic congestion
Objectives are aligned: ↓ system-wide vehicle miles, win-win-win
Ride-share Setting
Trip Announcement: Trips between origin - destination Role: driver, rider or flexible Participant wants to save $ At most: a single driver - a single rider No Transfers or multi-passenger trips
Announcement: Time Information
Announcement time
Departure time
Latest arrival time
direct travel timeflexibility
time window for matching
Lead-time
EarliestLatest
Relative to duration of trip?
Round Trips
Most trips in practice are round trips Announcement round trips: jointly or
separately? Rider may want assurance return ride before
departure Return trip alternatives?
System Dynamics
New announcements continuously enter and leave the system!
People leave becauseride-share was found Announcement expired
Effectively Handling Dynamics
Run optimization at specific time intervals; After a given number of announcements.
Optimization Engine: Input: trip announcements Output: driver-rider matches
Commit tentative match as-late-as-possible! shortly before latest departure of ride-share
Effectively Dealing with Dynamics
Effectively Dealing with Dynamics
Run 1
Expired
Effectively Dealing with Dynamics
Run 2
Ride-share finalized
Simulation Environment
Based on traffic model data from ARC
Ride-share Characteristics
Focus: Home-based Work, SOV Ride-share participation rate (bc 2%) Driver – Rider ratio (bc 1:1) Announcement lead-time (abs) (bc 30 min) Time flexibility (abs) (bc 20 min)
Announcement Generator
Randomly generate trip announcements based on o-d trip data:2024 Traffic Analysis Zones (TAZs)# work-related round trips per day: 2.96 million~ 87% single occupancy trips# O-D pairs: 2.90 millionmax # trips per O-D pair: 881min # trips per O-D pair: 0.01
Generate time information:
1. Home-work Draw latest departure: 7:30am, sd. 1h Calculate: earl. departure, lat. arrival,
announcement
2. Work-home Draw time at work: 8 hour, sd. 30 min Add time at work to announcement times
Announcement Generator cont’d
Ride-share Scenarios
SEPAR: separate announcements for round trip, no guaranteed ride back
JOINT: joint announcement for round trip, guaranteed ride back (not necessarily with same driver!)
BOUND: all daily trips known upfront (no dynamics)
Simulation Results
SUCCESS OUTWARD
(riders)
SUCCESS
RETURN
(riders)
∆ VHM ∆ TRIPS
SEPAR 76.4% 96.7% -28.7% -37.6%
JOINT 68.2% 100% -21.3% -33.7%
BOUND 75.0% 100% -24.0% -37.6%
-8.2! -0.6% of total trips
Sensitivity
Increase/ decrease participation rate
0.0
5.0
10.0
15.0
20.0
25.0
30.0
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90
SUCCES RATE
VH
M S
AV
ING
S
1%
2%
5%
More + better matches!
Sensitivity cont’d
Flexible roles → success rate ↑ ↑ time flexibility → success rate ↑ response time ↓ → success rate ↓ ↑ lead-time → success rate ↑
Cost savings
Total daily system-wide savings: $53,000 20% cut Ride-share provider: $10,600 Viable business model?
Avg. savings pp matched: $1.4 (20%) Enough incentive to participate?
Input: $0.55 per mile (AAA 2007)
Environmental benefits
System-wide vehicle-miles: -105,519 Vehicle Trips: -15,400
Emissions Hydrocarbons: -650 lbs/ day CO: -4000 lbs / day Oxides of Nitrogen: -323 lbs/ day
When can we find ride-shares?
0%
10%
20%
30%
40%
50%
60%
70%
80%
3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
departure time
succ
ess
rateDensity is good
What if we offer awards?
Subsidize ride-share by a fixed award per match
20.2
20.4
20.6
20.8
21.0
21.2
21.4
68.2 76.3 78.9
Success Rate
VH
M s
avin
gs
No award
Award = $0.55
Award = $1.10
$9,500 $19,000
+8% +2.5%
Under development
Study system performance over time Key observations:
New participants try ride-sharing Dissatisfied participants may stop announcing
trips
Inspired by innovation diffusion models: Inflow new users dependent on size of user pool! Outflow depends on cumulative success rate
Outlook
More realistic travel time settingsTime-dependent travel times
Behavioral modeling Match acceptanceCancelationsNo-showsChoices…
Thank You
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