Current Practices

TMS Characteristics

A survey was conducted in the spring of 2000 to gauge the use of CM by transportation agencies in the United States.1 The results indicate a need to educate the TMS community about CM in order to realize a significant commitment to this valuable resource-saving activity. The survey also revealed that many of the complex TMSs in this country are not using a formal change control process. This lack of formal change control processes calls into question the very integrity of many of these systems.

The first question of the survey asked about the core functions provided by the TMS. Respondents were to check all that applied, and if a particular agency performed more than one function, then the sample size would increase accordingly. Counting each function independently increased the sample size from 38 to 42. Figure 2 illustrates the percentage share of the functional classes of systems.

Figure 2. Use of CM According to TMS Function
Figure 2. Use of CM According to TMS Function D

A key finding of the survey was that a relatively low percentage of TMSs use CM. What was particularly notable is that only 27 percent of signal control systems and 62 percent of freeway management systems reported using CM.

Another clear trend in the survey responses is that the likelihood of a TMS using CM is dependent on the size of the system. Larger systems are more likely to utilize CM, as illustrated in figure 3.

Figure 3. CM Use by System Size
Figure 3. CM Use by System Size D

Benefits/Costs of CM

Most of the agencies responding to the survey reported that the benefits gained from CM were well worth the costs required. Table 1 presents the average survey rating for a series of CM benefits. The ratings were on a scale of 0 to 10, with zero representing no benefit and 10 representing the highest level of benefit. Note that according to the survey responses, the largest benefits of CM are seen in the ability to maintain systems and in improved system reliability.

Table 1. Average Benefits Ratings for CM (Scale: 0 – 10)
System Reliability System Maintainability Ability to Upgrade System Ability to Expand System Ability to Share Information with Other Systems Ability to Integrate with Other Systems
7.8 8.3 7.5 7.4 5.8 5.7

Finally, when asked to rate if the overall benefits of CM were well worth the costs, on a scale of 0 to 10 (with 10 being complete agreement, and 0 being complete disagreement), 77 percent of the agencies gave a rating of 7 or higher. Again, this strongly indicates that of the relatively small percentage of agencies using CM, the experience has been positive.

CM Benefit Testimonials

"With almost 20 years experience in the design, implementation, modification and expansion of our system, the benefits of quickly being able to recover from problems by returning to an earlier working state are enormous. Our system has been very dynamic, and there is always some area where we are working on an improvement or upgrade, while still actively managing traffic."

"As in any large, complex system, CM can provide a constant understanding of the current state of the system…. The key factor in CM is having a central repository of information for reference as personnel changes occur over the life of the system. It also is a great aid in maintaining the system when items are replaced for repair. Technicians should have ready access to configuration data when installing or re-installing standard system components."

"A formal, documented configuration control process can save operational costs over the life of the contract and mitigate the impact of personnel and equipment changes."

— Comments obtained from Spring 2000 survey of transportation agencies

1 This survey was originally conducted for an NCHRP Synthesis project. The full results of this project are published in NCHRP Synthesis 294 (2001).