Roadtrains

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Roadtrains
Presented by Bruce A. McHenry
Models by Dana Reynolds
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roadtrain
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Definition
roadtrain n 1 manually connected series of truck
trailers
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Coupling While Moving

• Traffic flow is uninterrupted
• No need to build large staging areas at major
  intersections
• No time-to-destination (TTD) penalty for using a
  roadtrain
• Starts by Extending Adaptive Cruise Control

Psyched out? Uncoupling while underway eases
transition
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Definition
roadtrain n 1 series of physically connected
vehicles that assemble and disperse while moving
2 manually connected series of truck trailers
v 1 the act of joining a roadtrain
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Other Roadtrain Attributes

• One or even two human pilots leading
• Would be increasingly supported by redundant
  safety systems

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Why Connect Vehicles?

• Full size sedans exceeding 100 MPG
• Vastly improved lane throughput (4-5X)
• Should improve safety (followers have no need for
  additional headway and cannot collide)

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Energy Consumption
Rated 26MPG on EPA highway
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Aero Drag 75 at Highway Speed
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Aerodynamic Drag in Platoons
Showing estimate of mid-vehicle correctionfor
rotating wheels.
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Chevy Lumina MPG Connected in Roadtrain
Solo 26MPG
Approximate improvement factor is1 / (.75 .6
.25) Roadtrain 36MPG
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Ideal Cars Have Smooth Junctions
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Front Shape Should Match Rear
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Guesstimate of Drag with Smooth Junctions
andWheels Included
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MPG of Aerodynamically Connected Vans
Solo 26 MPG 25 for rolling resistance (70MPH)
Improvement Factor Approximately 1 / (.75 .4
.25) 1.82 Streamlined van in roadtrain 47 MPG
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Hitching Improves Engine Efficiency
Average efficiency increases about 28/20 1.4X
Data reported here from Cleveland RTA
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MPG of Hitched, Streamlined Van
Streamlined van in roadtrain 47 MPG
If towed by engine operating near maximum
efficiency 1.4 47 66 MPG
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Replacing Combustion Engine Reduces Total Weight

• Replacing internal combustion engine with short
  range batteries may reduce curb weight 50
• 10 long vehicle could have same internal space
  as typical 16 sedan
• Assume gross weight reduced 40

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MPG of Connected, Streamlined All-Electric Van
Towed, streamlined van in roadtrain 66 MPG
If weight reduced by 40 66 / (.75 .6 .25)
73 MPG
Overall 26 MPG becomes 73 MPG
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Congestion Relief

• Human drivers have long reaction times and
  average at least .6 car length per 10 MPH
• Human drivers are quicker to brake than
  accelerate
• Human drivers are poor at anticipating lane
  closures and do not merge in a timely and orderly
  manner

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Human Pilot Required

• Highly qualified and properly insured human
  pilots in front will be needed for the
  foreseeable future (though assistance will be
  crucial to safety improvements)
• Fully robotic driving at low speeds also likely

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Piloting is Privilege, Likely Paid

• Subject to additional age and other restrictions
• Subject to extra testing and monitoring (e.g.
  reaction time testing, monitoring of alertness,
  speed and lane centering, distraction
  elimination, reports from followers)
• Pilots may receive compensation

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Secure Corridors Only

• Intersection collisions must be rigorously
  prevented
• One-way streets strongly preferred
• Perhaps permitted only where encouraged in HOV
  privileged lanes

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Heaviest Class First

• Heaviest vehicles usually have worst stopping
  characteristics
• Heavy vehicles will also tend to be locomotives
• Heavy vehicles best able to protect followers
  from collisions
• Heavy vehicles tend to be larger and afford their
  pilots best view of conditions ahead
• Lightest last reduces crushing forces on vehicles
  in the middle in the hopefully very rare pile-up

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Improving Safety
Safety is 1
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Modeling Risk
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Docking ACC Required

• D-ACC extends Cooperative Adaptive Cruise Control
  (C-ACC)
• 99.99999 reliable high speed communications
  channel using light
• Braking continuously re-calibrated using distance
  sensing

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Why Connect Vehicles?

• Full size sedans exceeding 100 MPG
• Vastly improved lane throughput (4-5X)
• Should improve safety (followers have no need for
  additional headway and cannot collide)
• Greatly reduces driving effort
• Key component of driverless taxis small freight
  vehicles
• Leads to electrification of the arterials

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Special Situations for ACC (Drafting Cruise
Control)

• Controls can be longitudinally yoked together but
  compression derailment can occur with
  differential braking capability. In general,
  making slowest braking vehicles lead prevents
  this EXCEPT
• ice/snow/dry
• wet/dry
• rough/smooth
• asphalt/concrete

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The Big Danger of Drafting

• Revealed Hazard Problem
• Leader changes lanes suddenly to reveal
  imminently obstruction to followers who are
  blocked by traffic in adjacent lane

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Solution

• Eventually integrate signaling and adjacent
  vehicle detection throughout the roadtrain
• Initially through correcting driver behavior
  signal with adequate time for drafting drivers to
  verify safety, duplicate signal (and give
  positive feedback)

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Enables Door-to-Door Driverless Services

• Low speed driverless vehicles already demonstrated

• Roadtrain driverless dramatically lowers cost
  of shared vehicles. Package delivery.

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Transit Vehicle Automation

• Drivers only on locomotives
• Vehicles running along transit routes must be
  able to join/leave passing roadtrain
• On-board vision system
• Infrastructure based hazard detection
• Passenger override
• Possible roadtrain pilot override

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Hetereogeneous Vehicles

• Bodies evolve towards an optimal shape starting
  with cars, trucks and vans much like what
  manufacturers are producing today

Nesting roadtrain cars withretractable 3rd wheel
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Benefits Summary

• triples fuel economy
• 5X lane capacity when needed
• Mostly driverless
• Enabler of automated D2D services
• Facilitates automation of transit with TTD
  comparable to private cars
• Lowest capital and operational costs
• Safety comparable to rail
• Leads to electrification and e-guideways

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Everybody Wins
(Almost) Everybody Wins

• Professional drivers get more pay
• Followers more than offset payments in
  convenience and fuel savings
• Manufacturers get to sell a whole new class of
  vehicles
• Battery makers win
• ICE makers lose

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Incremental Adoption

• Plausible Sequence
• Adaptive Cruise Control adapted for
  draftingBenefit fuel economy
• Priority lanes Benefit congestion relief
• Integrated inter-vehicle control includes
  steeringBenefit chauffeur mode
• Tow hitchBenefit fuel economy, low cost (all
  electric cars)
• Electrification of the arterialsBenefit more
  diverse and lower cost energy sources
• Addition of rail modeBenefit best ton-mile
  efficiency, less public cost