Briefing to the National Surface Transportation Infrastructure Financing Commission

Shelley Row

Director

ITS Joint Program Office

Research and Innovative Technology Administration (RITA)

Technology (Electronic Toll Collection or GPS plus 2-way communications) Makes Congestion Pricing Possible

Toll Tag Technology

GPS plus On-Board Units and

Wireless Communications

GPS plus On-Board Units and Wireless Communications

Tolling and E-Pricing

• Increasing interest in Electronic Toll Collection (ETC) and road/congestion pricing

– Most states have it for toll expressways

– Not all state systems are compatible or interoperable, but more are becoming so

• ETC can be expanded to incorporate congestion pricing through additional tag reading equipment

– Additional tag reading equipment placed over/alongside of roadway to read free-flowing traffic’s tags

– Uses back-office systems of same type already in place for ETC on toll roads

• Equipment for ETC may be used for other purposes, depending on the technology used

– E.g., speed measurement, such as in Houston, traffic counts if all vehicles have tags

– Payment of other facility usage charges, e.g., public parking lots

Limits of Current ETC Technology

• Amount of data transmitted is small

• “Intelligence” of technology resides in the back-office application

• Vehicle tags have little to no processing capability – limits what they can support

• Security is limited to encryption to support authentication and integrity (ensuring the appropriate party is billed)

– Other applications have additional security requirements, such as privacy

Types of Applications Using Wireless Communication with Vehicles

• Application Categories:

– Tolling / Pricing

– Safety

– Mobility

– Commercial Applications

• Each use wireless communications

• Each have their own set of communications and positioning requirements

Critical Factors Affecting All Types of Applications

• Positioning technology – many applications require knowledge of vehicle position, either relative to the road or other vehicles

– “Which road” (± 5-10 meters)

– “Which lane” (± 1 meter)

– “Where in lane” (± 30 centimeters)

– Current vehicle GPS systems are limited to “which road” accuracy

• Security – varying application requirements for privacy, authentication, access control, integrity, availability, and/or non-repudiation

– Encryption is just part of the solution

• Communications – varying application requirements for:

– Range

o Message size

o Latency

o Update rate

Approximate Requirements for Tolling and Pricing Applications

• Positioning: Typically “which road”, however for ETC, lane discrimination needed in order to bill the correct vehicle.

• Security: primarily integrity, and non-repudiation

• Communications:

– Range: short range desirable for ETC

(10’s – 1,00’s of meters), can vary for GPS-based approaches

– Message size: small (100 to few thousand bytes)

– Latency: can be high (so long as completed single transaction while within communications range)

– Update rate: low (multiple exchanges for reliability, but only need 1 actual transaction while passing toll reader)

– Reliability: high, in order to ensure accurate billing (>99.9%)

Approximate Requirements for Safety Applications

• Positioning: primarily “which lane,” with some applications requiring “where in lane”

• Security: includes privacy, access control, integrity, authentication, availability

• Communications – varying application requirements for:

– Range: short range desired, typically 50-500 meters

– Message size: small (100 to few thousand bytes)

– Latency: very low, typically 0.1 seconds or lower

– Update rate: typically 10x per second or higher

– Reliability: very high (safety of life)

Approximate Requirements for Mobility Applications

• Positioning: primarily “which road” although some applications require “which lane” (e.g., traffic counts by lane, speed discrimination between HOV & other lanes)

• Security: primarily privacy

• Communications:

– Range: No firm requirement, can vary by selected medium

– Message size: small to large (~100 bytes for probe data, >100K bytes for off-board navigation)

– Latency: moderate (seconds for signal control, higher for traveler information)

– Update rate: can be low (on the order of seconds to minutes)

– Reliability: moderate (lost messages are not a safety issue)

Requirements Summary

	Tolling / Pricing	Safety	Mobility
Positioning	Typically “which road”	Typically “which lane,” some “where in lane”	Primarily “which road”, some “which lane”
Security	Integrity and non-repudiation	Privacy, access control, integrity, authentication, availability	Privacy
Communications	Short-range for ETC, any for GPS Small messages High latency Low update High reliability	Short range Small messages Very low latency Very high update Very high reliability	Range can vary Small to large msgs. Moderate latency Low update Moderate reliability

Safety has the most stringent requirements

Communications Technology Options

Options	Tolling / Pricing	Safety	Mobility
Short range V2I comm. as currently used (e.g., EZ-Pass) Higher-end V2I and V2V comm. such as DSRC at FCC-provided 5.9 GHz band Cellular, mobile WiMax, etc.	Tag-based systems Tag-based or GPS based GPS based systems	N/A Required for low latency, high availability, secure safety comm. N/A	Very limited (travel time readers) Supports all applications, best match for some location-specific applications, e.g., signal control Supports many applications

Where multiple options exist, final deployment will depend upon trade-offs such as relative cost, complexity of in-vehicle equipment vs. infrastructure, commercial acceptance, etc., and may be a combination of technologies

Vehicle Infrastructure Integration Program

• Research on wireless communications capabilities to enable safety, mobility, and commercial applications

• Primary focus on enabling and advancing deployment of “active safety” capabilities

– Vehicle-to-vehicle applications

– Vehicle-to-infrastructure applications

• Multiple strategies possible for mobility and tolling/electronic payment applications

• Working with the OmniAir Consortium to develop a concept of operations for electronic payment systems

• Conducting SAFE TRIP 21 operational test to demonstrate current technology capabilities

Examples of Wireless Technologies

Technology	Range	Latency
5.9 GHz DSRC	1000 m	.0002 sec.
Digital Cellular	4000-6000 m	1.5-3.5 sec.
Bluetooth	10 m	3-4 sec.
Digital Television	40,000 m	10-30 sec.
Other 802.11 Wireless Technologies	1000 m	3-5 sec.
Terrestrial Digital Radio	30,000-50,000 m	10-20 sec.
Two-way Satellite	N/A	60+ sec.