Expressway  Traffic  Optimization 


Some members of the Intelligent Transportation Systems (ITS) industry are working to steer a connected-vehicle (CV) ITS future to depend on a radio frequency (RF) wireless communication technology foundation.

Transport authorities, the auto industry, computer and communication technology companies, are developing standards and trials for wireless RF vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) ITS.

Vehicles equipped with RF wireless on board units (OBUs) have shown applications communicating with each other and with wireless stationary roadside units (RSUs). More ambitious CV demos are active / planned.

The U.S. Department of Transportation (USDOT) has taken a leading role in trademarking and supporting development of the IntelliDrive® RF wireless V2V / V2I standard. Major RF wireless commercial carriers are promoting their latest 4G / LTE broadband services for ITS / CV uses.

Powerful interests are pushing hard with some apparent success, for U.S. federal legislation mandating IntelliDrive OBUs in new vehicles sold in that country. Justified primarily for safety reasons (reduce collisions).

The Congestion Challenge

A major weakness of RF wireless V2V / V2I communication foundations such as IntelliDrive is a lack of proposed applications with sufficiently attractive benefits to transportation users.

Traffic safety, the main selling point for IntelliDrive, comes second to traffic congestion as a grass-roots political issue. Happily, safety will significantly improve with a solution to expressway congestion.

The fundamental political problem with an ITS emphasis on traffic safety, is private car driver psychology. Most people who commute by private car expect to encounter traffic congestion EVERY DAY, they do not expect to encounter a collision on ANY DAY.

The massive collective cost of collisions is socialized by insurance. If the auto insurance sector can credibly promise major premium reductions, this would improve the political appeal of safety-focused ITS innovations such as IntelliDrive.

The huge cost of traffic congestion by contrast, is directly and daily paid by individual (voting) drivers, passengers and shippers.

So chronic traffic congestion on controlled access highways (freeways, motorways, expressways) is by far the number one political transport issue of concern to users of roads and highways.

Expressway congestion is also a most compelling ITS industry invention opportunity (and daunting political / business / technical challenge).

The Headway Challenge

Real-time control of individual vehicle headways is key to: best freeway traffic operation => end of congestion => peak effective safe traffic capacity => efficient use of highways => less road wear, big cuts in: trip times, fuel use, emissions, braking, rage, collisions.

RF wireless-based ITS communications e.g. IntelliDrive is an unsuitable foundation platform for reliable real-time vehicle headway management to end expressway congestion:

  • (IN) SECURITY -- Jamming (i.e. disrupt, not decode) ANY RF-based communications (e.g. IntelliDrive / GPS / cell / wireless) in a specific area is easy. Inject enough noise into the radio frequencies used, and communications fail. Is IntelliDrive immune?

  • (LOW) BANDWIDTH -- Real time micro-guiding individual vehicle headways on expressways, will require a constant ultra-low-latency flow of huge volumes of millisecond-resolution multi-sensor vehicle detection data. Aggregate data flow rates are likely to be in the GIGABYTES PER SECOND range. Are IntelliDrive bandwidth and latency adequate?

  • (SLOW) FLEET ADOPTION -- Vehicle owners, facing severe financial pressures, are keeping vehicles in service longer and longer (USA average 11 years). Payoff from ITS solutions like IntelliDrive, that need new (or retrofit) vehicles, will be AGONIZINGLY SLOW.

  • (WEAK) DETECTION SUPPORT -- GPS-based in-vehicle position-detection, has security, reliability and resolution issues. IntelliDrive roadside unit (RSU) devices could be modified to act as traffic detection sensor platforms, albeit less feasible sensor hosts, in both spacing and location, than ETO road-top signal / sensor heads.

  • (WEAK) AUTO SECTOR -- Is it really wise for the ITS industry to lead transport users, to depend on a fatally-delayed-recall-plagued struggling shrinking bailed-out automotive manufacturing industry, for a massive connected-vehicle future of mainstream real-time, mission-critical, safety-critical public / private ITS infrastructure?

ETO and IntelliDrive

An ETO ITS platform makes a compelling partner for IntelliDrive:

  • (HIGH) SECURITY -- Foundation ETO uses only visible light for all communications (fibre-optic and visible headway signals). Avoids exposure to disruption, by hostile parties who use simple spectrum noise jamming attacks, a weakness inherent in RF wireless comms.

  • (HIGH) BANDWIDTH -- Fibre-optic low-latency technology can reliably support huge data volumes produced, of high-frequency traffic detection data flowing in real-time, from sensors on the many 100,000s of ETO signal / sensor heads, on a large busy expressway network.

  • (INSTANT) FLEET ADOPTION -- ABSOLUTELY NO SPECIAL ETO VEHICLE EQUIPMENT REQUIRED. Every vehicle in the existing fleet is already compatible with ETO technology. ETO immediately works with every driver on the expressway network. Little driver training needed for ultra-easy intuitive luminous ETO headway signals.

  • (EXCELLENT) DETECTION SUPPORT -- Close spacing (10m / 33ft) and convenient lane centreline pavement location, make ETO signal devices ideal host platforms for traffic sensors. Each ETO signal / sensor head hosts multiple sensors. All heads together form a robust redundant pervasive millisecond-rate traffic detection array.

  • (BOOST) AUTO SECTOR -- ETO technology, simply by making all vehicles work MUCH better on expressways, will perceptibly boost auto industry fortunes. ETO will also INSTANTLY open up a HUGE MARKET for the ITS / automotive / RF wireless sectors to innovate value-added options, products and services for ETO. For example:

    • In-vehicle ETO-enabled adaptive cruise control (ACC) option, manages automatically the driver's headway decision-making, using signals from ETO signal / sensor heads in the roadway.

    • Extra ETO services using a variety of in-vehicle fixed and mobile devices will further personalize basic ETO, with instant traffic advice and eventually 100% automatic trip operation.

See ETO and RF Wireless, below for IntelliDrive / ETO synergy.

ETO and RF Wireless

An ETO ITS platform could become a partner for wireless RF service providers, by hosting carrier-end base station microized circuitry and antennas on pavement-embedded ETO heads acting as "antenna pads".

ETO RF "antenna pad" real estate leasing, would boost the ETO business case: IntelliDrive RSU, cell / smart phone, Bluetooth Internet access, other microized functions e.g. meteorological / environmental sensors.

There are technical challenges with short-term RF links between fixed road-top devices and fast moving vehicles. However, the potential for 100,000s of ETO heads in the pavement of a large expressway system, to RF-connect expressway travellers to the wider world, is intriguing.

Enthusiasm for increased use of RF radiation energy for vehicle wireless comms, perhaps should be moderated in recognition of occasional but persistent mass media reports of perceptible adverse effects, from nearby sources of RF energy (e.g. WiFi router in classroom, bedroom).

Vehicular Visible Light Data Communications

Visible light communications (VLC) is another potential means for data communications between moving vehicles and road-top devices.

VLC is a proven technology using low-cost LEDs and photodiodes, offering massive bandwidth potential for e.g. Internet / media access.

Here are quotes from a June 2010 vehicular VLC research M.Sc. thesis:

  • "In this thesis, we make the case for the use of vehicular VLC (V2LC) and address the unique capabilities and limits of V2LC with respect to the requirements of the vehicle safety and internet access applications.

  • "We describe an architecture of V2LC networks, in which vehicle lights as well as infrastructure lighting serve as transmitters, and receivers are co-located with the transmitters, and identify five network services V2LC needs to provide for the vehicular applications.

  • "VLC can be applied in vehicular environments since there already exists an infrastructure with many vehicle lights and traffic lights installed with LEDs.

  • "While RF solutions to the vehicular applications have been proposed ... their capabilities to meet the requirements of the vehicular applications are still an open problem.

  • "VLC uses the visible light spectrum (between 400 THz and 790 THz) as the communication medium. A VLC system consists of VLC transmitters and receivers, which are physically different and functionally separated.

  • "The transmitter modulates information at lighting sources, such as LEDs. This modulation takes place in such high frequencies that humans' bare eyes cannot perceive any difference in lighting compared to that when there is no modulation.

  • "A VLC receiver consists of photodiodes either as stand-alone elements or in the form of an image sensor.

  • "A VLC system inherits four advantages in data transmission from operating in the visible light spectrum and functioning with LEDs and photodiodes.

    • "First, VLC is secure for data contents because it often requires a line-of-sight for transmission and reception.

    • "Second, VLC is safe to humans and other instruments because it operates in the visible light spectrum and in low density with lighting devices.

    • "Third, VLC is cost-efficient because its components, such as LEDs and photodiodes, can be massively produced, and it is additionally power-efficient by using LEDs.

    • "Fourth, VLC has a ubiquitous infrastructure support because it can use the existing lighting infrastructure that is deployed everywhere.

  • "We show that V2LC is resilient against visible light noise and interference, and it can enable full-duplex mode. Further, we show that V2LC can satisfy the stringent reachability and latency requirements in dense vehicle traffic conditions.

("The Case for Vehicular Visible Light Communication (V2LC): Architecture, Services and Experiments", by Cen Bi Liu, Rice University, Houston, Texas, June, 2010)

ETO and V2LC

The LEDs in ETO heads used for visible light headway signaling to drivers, could simultaneously perform VLC data transmission to vehicles with no perceptible impact on visible signal appearance to drivers.

ETO heads will also be equipped with video image sensors and simple photodiode sensors, for traffic detection. These same components could support reception of VLC data from vehices.

"infrastructure lighting" (quoted above) presumably refers to roadway lighting from poles and other structures. "traffic lights installed with LEDs" (quoted above) presumably are traffic intersection signals.

The research paper does not specifically refer to VLC "infrastructure [i.e. stationary] nodes" being embedded in roadway pavement.

The following quotes from the paper reveal one issue that would be relevant to the feasibility of V2LC service for ETO heads:

  • "We find that V2LC is resilient against wideband noise sources (i.e., sunlight) with the exception of a direct exposure to the sun, which can only occur when vehicles with a direct line-of-sight to the sun and during sunrise and sunset (i.e., when the sun makes a small angle to the horizon and falls into the VLC receiver's 12° field-of-view angle).

  • "We also find that V2LC is robust to narrowband noise that is generated by idle VLC transmitters as well as legacy lights with no data transmission abilities.

  • "Noise can affect V2LC's performance by saturating the photodiode. This happens only if the noise power is significantly high, e.g., direct exposure to sunlight and close range of 5 m within a halogen light bulb, and the noise source directly falls in the field-of-view angle of the receiver.

  • "With increasing distance between the noise source and the receiver and decreasing the field-of-view angle, V2LC becomes completely robust to both wideband and narrowband noise, e.g., sunlight and idle LED lights.

It may turn out that ETO heads will require separate image sensors and photodiodes, dedicated to V2LC, facing vehicle rear lights, to avoid noise from halogen headlights and low-horizon sunlight.

The need for a lens self-cleaning function for ETO signal / sensor heads will be addressed during the ETO feasibility investigation.

eto_intellidrive.htm -- 4 August 2014

Copyright(c) & TMs 2011- 2014 ITS-ETO Consortium

Website Policy