Chapter 5. Evaluation of ID Methods

Based on the identified ID methods discussed, an evaluation matrix was created to compare the performance of each in various areas. A grading system was used to create the evaluation matrix. Grades were based primarily on a review of literature, and a review of manufacturer specifications. Participation in various demonstrations, and input from the expert panel through consensus also informed the grading.

The performance areas are listed in this chapter and describe the background and reasoning behind the grading provided for each ID method. An evaluation matrix summarizes the grading to facilitate the selection of an ID method based on each performance area.

Transportation agencies can use the evaluation matrix in this chapter to select their preferred ID method. Each method has strengths and weaknesses. Selecting a preferred ID method is greatly dependent on the agency’s needs. Beyond the evaluation matrix, it is important to quantify the cost and scale of implementation of the ID method to determine feasibility.

EVALUATION APPROACH

As previously discussed, the three primary ID methods are:

• 1D or 2D barcodes (printed on the hardware and as tag identifiers).
• Passive or active RFID (as tag identifiers).
• Serial numbers (printed, stamped, and in combination with barcode tag identifiers).

These primary methods all have various attributes that may or may not impact an overall rating. Methods were graded based on their best commercially available option for that attribute.

Performance Areas Evaluated

This chapter summarizes information about how the ID methods were evaluated, along with the results of the evaluation. The ID methods are evaluated for their ability to:

• Convey data.
• Withstand roadside conditions.
• Connect to existing systems.

The issues for method selection, discussed in the previous chapter, informed the evaluation of the ID methods for each of these three aspects. Cost is also a factor for agencies to consider alongside performance. It was not evaluated separately because the cost varies significantly based on the desired performance and quantity. The following performance areas address these three aspects:

• Convey data:
  • Information storage capacity.
  • Read distance.
  • Read rate.
  • Line of sight and angled reading.
  • Automation and mobile reading.
  • Read/write options.
  • Event trigger options.
• Ability to withstand roadway conditions:
  • General roadside durability.
  • Vandalism-related durability.
  • Maintenance activities.
  • Crash event durability.
• Ability to connect to existing systems:
  • Connectivity.
  • Equipment needs.
  • Software needs.
  • Information security.

Grading

A five-level grading system was used:

• Poor–the method provides minimal or no performance.
• Fair–the method provides low performance.
• Good–the method provides acceptable performance.
• Very good–the method provides above-acceptable performance but has some disadvantages.
• Excellent–the method provides above-acceptable performance and has only minimal disadvantages.

An excellent grade suggests the highest capability, while a poor grade suggests minimal capability in the corresponding performance area.

EVALUATION RESULTS

Each of the performance areas are discussed in the following sections with some detail regarding how the various ID methods performed. The evaluation results for all methods by performance area are presented in the evaluation matrix (table 2). The table is useful to easily compare the capabilities of each ID method.

Information Storage Capacity

The information storage capacity performance area primarily considers the number of printed characters or matrices and electronic data. Typically, one character is 8 bits.

The 1D barcodes allow up to 48 characters or approximately 384 bits, and 2D bar codes allow up to 4,296 characters or approximately 34 KB. Passive RFID allows up to 64 KB, and active RFID allows up to 128 KB. Serial numbers have no electronic data storage on the tag, and the tag size determines the available area for printed information.

Read Distance

The read distance performance area considers the maximum distance a user can read information from a selected ID method without considering line-of-sight requirements.

The 1D barcode tag identifiers generally have reading distances of less than 15 ft. (5 m), and the reading distance depends on tag size and scanner settings. The 2D barcode tag identifiers have maximum scanning distances that are approximately half the distance of 1D barcode tag identifiers. Passive RFID tag identifiers have reading distances that approach 100 ft. (33 m). Active RFID tag identifiers have reading distances that approach 300 ft. (100 m) due to beacon-like signals from internal power sources. Serial number identifiers have reading distances limited to the human eye or photo magnification, and the reading distance depends on the size of the tag.

Read Rate

The read rate performance area evaluates the number of tags that users can read over a given period of time, excluding distance but including line-of-sight considerations.

The 1D barcode scanners can read one tag per scan and are limited by line of sight and a successful scan. The 2D barcode scanners can read one tag per scan and are limited by line of sight and a successful scan; 2D barcodes generally take a longer time to scan. Both passive and active RFID tags can be read in many multiples per scan, up to 100 tags at once, with appropriate middleware. Serial number identifiers are limited to a single manual read and limited by line of sight.

Line of Sight and Angled Reading

The line-of-sight and angled reading performance area evaluates the method’s line-of-sight requirements for scanning and reading tags without consideration for reading distance.

The 1D barcode tag identifiers require direct line of sight and proper alignment of tag and scanner lasers. The 2D barcode tag identifiers can be read at an angle but still require partial line of sight. Passive and active RFID tag identifiers can be read within the reader’s generated magnetic field and do not require direct line of sight. Serial number identifiers must be read manually, and line of sight is required.

Automation and Mobile Reading

The automation and mobile reading performance area evaluates the ability of users to read ID tags automatically with consideration for mobile tags or readers and reading distance.

The 1D barcode tag identifiers require the barcode and scanner to be aligned. The 2D barcode tag identifiers offer some allowance for misalignment with angled scanning, but the tag has to be fairly close to the scanner. Passive RFID tag identifiers can be read automatically and while the reader or tag is moving. Active RFID tag identifiers can be read automatically while the reader or tag is moving; with the beacon function, they can be used to capture all tags within a radius of the reader. Serial number identifiers are limited to human interaction.

Read/Write Options

The read/write options performance area evaluates the available choices for reading and placing information on the selected ID method and does not include consideration for use with a connected database, only what information users can read from or add to the physical tag.

The 1D barcode tag identifiers are print (write) once, read only; some basic barcode types have character limitations. The 2D barcode tag identifiers are print (write) once, read only. Passive and active RFID tag identifiers are available in read-only; write-once, read-only; read/write; read/write with locking; and kill options. Serial number identifiers are write once, read only (non-electronic).

Event Trigger Options

The event trigger options performance area evaluates the ability of users to associate tags with additional electronic sensors, such as an accelerometer, without consideration for reading distance.

The 1D and 2D barcode tag identifiers have no event trigger options. Passive and active RFID tag identifiers have event trigger options but require reading of the tag. Serial number identifiers have no event trigger options outside physical damage.

General Roadside Durability

The general roadside durability performance area evaluates the ability of commercially available ID methods to withstand roadside conditions, such as temperature; exposure to moisture, wind, and abrasion; ultraviolet degradation; and roadside chemicals as described in a review of roadside conditions and manufacturer specifications. This evaluation does not include the need for maintenance or vandalism/crash event durability.

All ID methods and tag identifiers have options available to withstand all common roadside conditions.

Vandalism-Related Durability

The vandalism-related durability performance area evaluates the potential threat of vandalism including removing a tag, defacing a tag, or attempting to destroy an installed tag.

The 1D and 2D barcode tag identifiers can be found with stain-resistant properties, but barcodes could be obstructed or physically damaged. Passive RFID tag identifiers have impact-resistant properties (encasements) available and can be disguised as a hardware component or obstructed by reflective tape. Active RFID tag identifiers are not permanent since batteries need to be replaced periodically; the tag identifiers are also bulky, potentially limiting concealment options. Stain-resistant serial number identifiers are available, but tags could be obstructed or physically damaged; for example, stamped serial numbers could be filed off.

Maintenance Activities

The maintenance activities performance area evaluates the need for maintenance after installation and considers the best available attachment methods, plus resistance to staining and smearing.

The 1D and 2D barcode tag identifiers are stain resistant but may need cleaning before scanning. Passive RFID tag identifiers have no maintenance requirements if operating within specifications. Active RFID tags need to be replaced every 3 to 5 years due to battery life. There have been some advancements in battery life, with some manufacturers claiming a 10-year battery life. There is no easy way for a transportation agency to determine when battery life has ended. Like barcodes, serial number identifiers are stain resistant but may need cleaning before reading.

Crash Event Durability

The crash event durability performance area evaluates performance during and after a crash event, including forced dislodging of tags from roadside safety hardware.

The 1D and 2D barcode tag identifiers are available with resistance to abrasion, but crash events could damage the surface, rendering it unreadable, and there is no recovery option outside manually locating dislodged tags. Passive RFID tag identifiers are available with impact resistance, and dislodged tags can be found with readers and a proximity scan. Active RFID tag identifiers are available with rugged encasement; dislodged tags can be found with a proximity reader, and beacon tags can send out an active signal to help locate them. Serial number tag identifiers are available with resistance to abrasion, but crash events could damage the surface, rendering it unreadable; there are no recovery options outside manually locating dislodged tags.

Connectivity

The connectivity performance area evaluates the ability to connect with existing systems.

The 1D barcode tag identifiers have maximum character limitations that could prevent the use of existing asset identifiers; however, 1D barcodes can be read electronically, and users can connect scanners to the server database. Similarly, 2D barcode tag identifiers and both passive and active RFID tag identifiers can be read electronically, and users can connect scanners/readers to the server database. Serial number tag identifiers require manual input into a connected server database interface.

Equipment Needs

The equipment needs performance area evaluates the need for equipment to access the information on a tag. The evaluation method does not consider tools required to install tags.

The 1D and 2D barcode tag identifiers require a separate scanner although many available cell phone applications can read barcodes. The 1D barcodes also allow for the ID number to be printed (on a combined tag) under the barcode. Barcodes in general also require an interface for database connectivity. Passive and active RFID tag identifiers require a separate reader and an interface for database connectivity. Serial number tag identifiers have no immediate equipment requirement but require an interface (laptop) for database connectivity.

Software Needs

The software needs performance area evaluates the need for software for users to operate the ID method beyond onboard reader software and existing asset management software.

The 1D and 2D barcode tag identifiers require a server connection. Passive and active RFID tag identifiers require middleware for a server connection. Serial number identifiers require no software, but software may be needed to input and/or access data.

Information Security

The information security performance area evaluates how secure safety hardware information is once placed on the tag or when transportation agencies use a tag to connect to a back-end server database. This performance area does not evaluate physical tag security (discussed separately as vandalism).

The 1D and 2D barcode tag identifiers can be read by any scanner set to a specific barcode type, but users can encrypt identifiers, and back-end security may be necessary to prevent unauthorized access. Passive and active RFID tag identifiers can be read by any RFID reader (at greater distances for active RFID tags), but users can encrypt identifiers in the back end and/or lock writable memory blocks. If active RFID tags are used for greater storage, information exposure is a concern because tags can be geo-located using GPS. Serial number identifiers can be read by anyone, but without connectivity, security threats are isolated to the back-end interface where back-end security may be necessary to prevent unauthorized access.

CHAPTER SUMMARY

The ID methods were evaluated and graded for their ability to convey data, withstand roadside conditions, and connect to existing systems. The results of the evaluation allow transportation agencies to determine which ID method is best suited to their purpose. The evaluation showed the investigated ID methods to be adaptable to a transportation agency’s needs, once these needs are identified. The next chapter summarizes the findings included in this report.