6.0 Improvement Scenarios

6.1 Overview

This section presents signal system improvement scenarios which address common signal system deficiencies as indicated by the state-of-the-practice review (summarized in Section 3.0). These scenarios are used to explore how the elements of the SSAMS defined in Section 5.0 might be used to identify and prioritize improvement needs, and compare alternatives for addressing them with respect to goals, objectives, and performance measures.

Three different scenarios are described, representing conservative, moderate, and aggressive signal system improvements that address the identified deficiencies. For each scenario, a rough analysis of costs and benefits are provided for each scenario. Then, tradeoffs across the different scenarios are discussed.

The following references were used to assist in identification of scenario elements, and produce estimates of their costs and benefits. Note, however, that the emphasis of this analysis was not on presenting an accurate assessment of the benefits and costs of alternative strategies, but rather on illustrating the kind of tradeoff analysis that would be supported by a SSAMS.

Traffic Signal System Improvement Program, 2003 Update, Denver Regional Council of Governments, Adopted July 16, 2003.
Traffic Signal Operation Self Assessment, developed by the National Transportation Operations Coalition of the Institute of Transportation Engineers, 2004.
NCHRP Synthesis 307, Systems Engineering Processes for Developing Traffic Signals Systems, prepared by Dunn Engineering Associates, 2003.
Vancouver Area Smart Trek – Initiative 5 – Traffic Signal Systems (http://www.vastrek.org/initiatives/TS.htm).

6.2 Signal System Improvements

Table 6.1 presents a listing of signal system improvements that was developed to assist the process of constructing scenarios. The table classifies each improvement as “operations,” “preservation,” “upgrade,” or “reactive repair” for consistency with the signal system characteristics illustrated in Figure 3.1. Note that this list is not intended to be exhaustive, but rather illustrative of the major types of improvements that are considered by signal system operating agencies.

Table 6.1 Signal System Improvement Options and Impacts

Description	Category	Alternatives	Impacts
1. Signal re-timing, timing coordination	Operations	Adjust as needed based on complaints and observation, resources-permitting. Review and adjust timing for priority intersections, identified based on location (e.g., primary corridors), land-use changes, other changes affecting traffic patters. Review and adjust timing for each intersection once every three to five years.	Decrease user delay. Increase throughput. Reduce fuel consumption.
2. Implement weekend/ holiday timing plans	Operations	Implement for centrally controlled signal systems only. Phase in for isolated signals. Implement for all signals.	Decrease user delay. Reduce fuel consumption.
3. New equipment/ hardware/ software, for improved coordination and control	Upgrade	Alternatives would consist of different sets of locations for implementation of one of the following types of upgrades: Simple time-based coordination (TBC), Interconnected control (IC), Traffic Responsive Control (TRC), and Adaptive Control (ATC). A wide range of design and technology choices exist within each of these categories (e.g., detector types, controller types, software, communications equipment, etc.).	Decrease user delay. Increase throughput. Reduce fuel consumption. Reduce operational requirements (all but TBC allow for downloading of timing plans and adjustments, remote monitoring of intersection and equipment status) – though some technology choices will also add to staff training requirements or require specialized services to maintain Reliability (varies based on technology choice).
4. New equipment for preemption/priority	Upgrade	Vary number of railroad crossings with preemption. Vary extent of system with emergency vehicle preemption, and the types/numbers of vehicles to be equipped. Vary extent of transit routes covered by transit preemption/priority.	Decrease probability of rail-vehicle collisions (for railroad crossing preemption). Improve response time for emergency vehicles (for emergency vehicle preemption). Decreased passenger travel time and improved transit reliability (for transit priority).
5. Signalize additional intersections	Upgrade	Vary lead time for implementation for locations meeting signal warrants – prioritize based on funding availability, urgency of need.	Decrease crash rates/prevent crashes. Decrease user delay. Increase throughput. Reduce fuel consumption.
6. Replace bulbs with LEDs	Upgrade	Replace in conjunction with upgrades. Proactively convert older equipment only. Proactively convert entire system (vary number of replacements per year).	Reduced energy costs. Reduced signal failures/down-time. Reduced staff maintenance time requirements due to increased life.
7. Modernize controllers	Upgrade	Replace older controllers (varying criteria based on age, reliability, functionality, compatibility).	Improve reliability/reduce down-time. Reduce operational requirements.
8. Modernize detectors	Upgrade	Replace older loop detectors with newer technologies – e.g., video, ultrasonic (varying criteria based on age, requirements).	Improve monitoring capability. Reduced traffic disruption for maintenance.
9. Modernize signal heads	Upgrade	Replace older signal heads with longer lasting design (vary criteria, number of replacements per year).	Improve reliability/reduce down-time. Reduced staff maintenance time requirements due to increased life.
10. Preventive Maintenance on signal poles/structures	Preservation	Painting (at varying time intervals or age/condition thresholds). Inspection and Replacement/ Rehabilitation (at varying intervals or age/condition thresholds).	Increase useful life. Reduce risk of failure and associated emergency response needs.
11. Preventive Maintenance on Signal Heads	Preservation	Inspection and maintenance/ replacement (at varying time intervals or age/condition thresholds).	Increase useful life. Reduce risk of failure and associated emergency response needs.
12. Preventive Maintenance on Controllers and Detectors	Preservation	Inspection and maintenance/ replacement (at varying time intervals or age/condition thresholds).	Increase useful life. Reduce risk of failure and associated emergency response needs.
13. Make staff available to respond to problem reports	Reactive Repairs	Handle emergency requests only with existing staff. Add staff or contract out for improved response time and accommodation of non-emergency requests.	Improved customer service. Reduced delay. Improved safety.

From the state-of-the-practice review, the types of signal improvements rated as high priority by more than 40 percent of respondents included:

Replacing/repairing equipment;
Upgrading communications equipment;
Adjusting or upgrading existing signals;
Integrating signals within the agency’s jurisdiction (as opposed to coordination with other jurisdictions); and
Increasing operation and maintenance staff.

No direct questions on deficiencies were included in this review, but the following three can be inferred from these stated needs:

Signal down-time due both to older equipment and limited staff;
Signals operating with suboptimal timing plans, resulting in avoidable customer delay and excess fuel usage; and
Isolated Signals (not under closed loop operation), which increases maintenance costs (since timing adjustments cannot be downloaded from a central location), and makes coordination more difficult.

The next section describes how the elements of a SSAMS would help to identify these deficiencies. Then, Section 6.4 presents scenarios that address these deficiencies drawing upon the alternatives in Table 6.1.

6.3 Using the SSAMS to Identify Deficiencies

Signal Down-Time

Information on signal down-time would be derived from Trouble Reports, Work History Records, or, where they exist, from signal management software that automatically tracks equipment status (Real-Time Signal Status Information – archived or summarized). The Performance Monitoring functional component of the SSAMS takes information from Trouble Reports, Work History Records, and Real-Time Status Information from the signal system itself, and provides input to the Deficiency Analysis component. Ideally, the Deficiency Analysis capability would allow for analysis of patterns in failures that would help the SSAMS user to understand causes of failures and identify and prioritize appropriate actions. Information of interest would include:

Map of signal malfunction or failure rates by subsystem/location;
Signal component failure rates and mean time between failures by component type/model and age category;
Signal malfunction or failure rates by cause (e.g., bulb, controller, power outage);
Estimated number of vehicles affected by each signal failure cause – to help establish priorities for targeting preventive maintenance;
Mean time to repair for different types and models of signal components; and
Mean time to repair for different types of repair (e.g., by type or level of expertise required) – to identify where staff resources need to be supplemented.

Suboptimal Timing Plans

Information on which signals may need retiming can be derived from periodic floating car speed studies, reported complaints (the SSAMS Trouble Reports data component), or direct observation. In addition, Work History records that show when signals at each intersections were last timed, together with information from traffic monitoring systems on AADT growth (or development tracking systems) can be used to identify locations where analysis is warranted. Intersection crash data would also be of value to identify where safety issues related to signal timing may exist. Centralized access to information on current timing plans (in the SSAMS Operating Parameters data component) provides useful input to this process as well.

Isolated Signals

The SSAMS Intersection Inventory component tracks which signals are interconnected. This Intersection Inventory should include designations of functional system, priority corridors, and other defined roadway classifications that would help in prioritizing locations for extending existing or implementing new closed-loop systems. It should also (perhaps in conjunction with a Geographic Information System) allow for access to information on signal separation distances, and traffic volumes and turning movements. This would allow the SSAMS Deficiency Analysis component to perform automated screening based on defined criteria to identify where additional coordination should be investigated.

6.4 Scenarios

Overview

Three scenarios were developed to address the deficiencies discussed above: conservative, moderate, and aggressive. The conservative scenario emphasizes lower-cost actions and upgrades to address the most pressing deficiencies. The aggressive scenario takes a longer-term view, and pursues technology upgrades that will reduce the ongoing maintenance and operation cost of the system, and provide increased functionality and control that can be used to deliver improved performance. The moderate scenario takes the middle ground between the other two scenarios. All of the scenarios are for investments over a five-year period.

Improvements

Table 6.2 summarizes the improvements included in each scenario, organized according to the deficiencies that they address.

Table 6.2 Signal System Preservation and Improvement Scenarios

Deficiency	Conservative	Moderate	Aggressive
Signal Down-Time	Conduct annual inspections on all signals that have not been replaced or upgraded for the past seven years, and repair or replace any components that appear to be at the end of their life. Replace bulbs with LEDs at 30 locations, in conjunction with replacement of signal faces that are at the end of their life. Delay work on proactive inspections in order to respond to emergency requests.	Inspect each signal once every other year and repair or replace any components that appear to be at the end of their life. Convert half of the system to use LEDs (300 bulbs). Upgrade controllers and communications equipment in the most heavily traveled corridor (25 locations). Add another signal maintenance technician in order to improve response time to signal malfunction reports.	Conduct annual inspections of each signal and repair or replace any components that appear to be at the end of their life. Convert entire system to use LEDs (600 bulbs). Replace 100 older plastic signal heads with aluminum die-cast heads. Upgrade controllers and communications equipment at 50 locations along designated major corridors. Commit to a one-hour response time policy for any signal malfunction based on real-time tracking and external reports – negotiate a contract to provide this service.
Suboptimal Timing Plans	Conduct detailed retiming studies for 50 intersections each year, selected based on frequency of complaints and known changes in traffic patterns (due to new developments).	Conduct screening-level review signal timing for each intersection once every other year to determine the need for timing adjustment. Conduct detailed retiming studies for 75 intersections each year.	Conduct screening-level review signal timing for each intersection twice per year to determine the need for timing adjustment. Conduct detailed retiming studies for 150 intersections each year.
Isolated Signals	Add 10 new intersections to existing closed-loop systems.	Upgrade equipment at/between 50 additional intersections to bring them under closed-loop control.	Upgrade equipment at/between 100 additional intersections to bring them under closed-loop control and connect them to TMC.

Deficiency

Conservative

Moderate

Aggressive

Signal Down-Time

Conduct annual inspections on all signals that have not been replaced or upgraded for the past seven years, and repair or replace any components that appear to be at the end of their life.

Replace bulbs with LEDs at 30 locations, in conjunction with replacement of signal faces that are at the end of their life.

Delay work on proactive inspections in order to respond to emergency requests.

Inspect each signal once every other year and repair or replace any components that appear to be at the end of their life.

Convert half of the system to use LEDs (300 bulbs).

Upgrade controllers and communications equipment in the most heavily traveled corridor (25 locations).

Add another signal maintenance technician in order to improve response time to signal malfunction reports.

Conduct annual inspections of each signal and repair or replace any components that appear to be at the end of their life.

Convert entire system to use LEDs (600 bulbs).

Replace 100 older plastic signal heads with aluminum die-cast heads.

Upgrade controllers and communications equipment at 50 locations along designated major corridors.

Commit to a one-hour response time policy for any signal malfunction based on real-time tracking and external reports – negotiate a contract to provide this service.

Suboptimal Timing Plans

Conduct detailed retiming studies for 50 intersections each year, selected based on frequency of complaints and known changes in traffic patterns (due to new developments).

Conduct screening-level review signal timing for each intersection once every other year to determine the need for timing adjustment.

Conduct detailed retiming studies for 75 intersections each year.

Conduct screening-level review signal timing for each intersection twice per year to determine the need for timing adjustment.

Conduct detailed retiming studies for 150 intersections each year.

Isolated Signals

Add 10 new intersections to existing closed-loop systems.

Upgrade equipment at/between 50 additional intersections to bring them under closed-loop control.

Upgrade equipment at/between 100 additional intersections to bring them under closed-loop control and connect them to TMC.

Scenario Costs and Benefits

The SSAMS business processes for evaluation of candidate preservation and improvement options involves looking at each of the improvements in Table 6.2, and estimating both benefits and costs. A detailed calculation of benefits and costs is beyond the scope of this project, but Tables 6.3 and 6.4 provide sample formats for the output of such an analysis, as a concrete illustration of what a SSAMS would produce.

Table 6.3 Scenario Costs

Cost Component	Conservative	Moderate	Aggressive
Capital Costs – Capital Equipment	$57,100	$493,500	$1,342,000
Annual Costs – Engineering/Design Costs	$132,500	$290,000	$710,000
Annual Costs – Scheduled Annual Maintenance and Operations Staff Labor Costs	$128,000	$130,700	$112,100
Annual Costs – Emergency Annual Maintenance and Operations Staff Labor Costs	$10,400	$9,300	$8,000
Annual Costs – Maintenance Contract Costs	$0	$0	$150,000
Present Value	$1,138,800	$2,210,400	$5,255,300

Note: Present value was calculated for a five-year analysis period, using an eight percent discount rate. All capital costs were assumed to be incurred in the first year.

Assumptions used to calculate costs were as follows (these would be part of the Life-Cycle Costing and Budgeting components of the SSAMS):

Average annual salary for maintenance and operations technicians: $30,000;
Average cost to convert a signal to use LED: $485;³
Average per intersection cost of a contract for traffic study and signal retiming: $350;⁴
Average cost per location to upgrade controller and communication equipment: $2,500;⁵
Average labor cost per signal inspection: $200; and
Average equipment replacement/parts costs per signal inspection: $60.

Scenario benefits are assessed with respect to a set of performance indicators, as shown in Table 6.4.

Table 6.4 Scenario Benefits

Benefit	Conservative	Moderate	Aggressive
Reduced annual vehicle hours of delay due to improved signal timing.	5% [405,000]	8% [648,000]	15% [1,215,000]
Reduced annual gallons of fuel consumption due to improved signal timing.	3% [420,000]	5% [700,000]	9% [1,260,000]
Average annual reduction in the number of hours of signal down-time.	2%	13%	25%
Annual reduction in electricity costs.	14% [$3,200]	45% [$10,600]	90% [$21,300]
Decrease in the average number of crashes.	4% [113]	6% [169]	12% [339]

Assumptions used to calculate benefits were as follows (these would be part of the Improvement Analysis component of the SSAMS):

Average annual electricity costs per signal.⁶
- With conventional bulbs: $117.
- With LED: $11.
Average accident reduction per intersection retimed: 10 to 15 percent.⁷
Mean time between failures for signal controllers.
- Greater than or equal to 10 years old: six months.
- Less than 10 years old: one year.
Mean time between failures for bulbs.
- Conventional, less than five years old: one year.
- LED, less than or equal to seven years old: five years.
Reduced vehicle hours of delay per re-timed signal: 15 percent.⁸
Reduced fuel consumption per re-timed signal: nine percent.⁹

Key Tradeoffs Across the Scenarios

The comparison of costs and benefits across the three scenarios shown in Tables 6.3 and 6.4 allows the decision-maker to tradeoff the additional costs of the Moderate and Aggressive scenarios against the performance gains that they are expected to achieve. As shown, the Moderate scenario requires $1,071,600 more than the Conservative scenario, but results in improved reliability, and significantly reduced costs to motorists – in terms of both time savings and fuel cost savings. It also lowers the ongoing utility costs of the system. The Aggressive scenario costs an additional $3,044,900 over the Moderate scenario, but yields even greater levels of system reliability, motorist cost savings, and utility costs.

In addition to the benefits shown in the table, other performance indicators that are more straightforward to calculate and could be used to contrast the scenarios include:

At the end of the five-year period, percent of signalized intersections on major corridors that are under closed-loop control at the end of the five-year period – for these scenarios, 31 percent, 41 percent, and 53 percent, respectively;
At the end of the five-year period, percent of signalized intersections on major corridors that have controller, communications, and detection equipment with capabilities for Traffic Responsive Control – for these scenarios, five percent, 11 percent, and 17 percent, respectively;
At the end of the five-year period, percent of signals that have been converted to use LEDs – for these scenarios, 15 percent, 50 percent, and 100 percent, respectively;
Percent of signals that have been retimed within the five-year period – for these scenarios, 37 percent, 56 percent, and 100 percent, respectively; and
Number of intersections per maintenance technician over the five-year period (ITE recommends 30 or fewer, considering both in-house and contract forces) – for these scenarios, 41, 37, and 30, respectively.

This sample analysis has illustrated application of the principles of asset management to signal systems, using the framework developed for a SSAMS in Section 5.0. A similar type of analysis could be constructed to examine tradeoffs across different activity types – for example, an aggressive program of signal re-timing versus a focus on reducing signal down-time through equipment upgrades. Several scenarios could be defined, each with the same budget level but a different mix of work in order to explore what resource allocation yields the highest level of benefits.

After defining the SSAMS capabilities in Section 5.0, we observed that many of these are provided by systems already in place – e.g., for maintenance management and signal control. However, a number of the required capabilities – e.g., for life-cycle costing, are not commonly available. Because many of the required elements of a SSAMS are similar to elements of relatively mature asset management systems for infrastructure and for information technology (IT), the next section explores these types of asset management systems. It contrasts their capabilities to those required for signal systems asset management, and suggests ways in which future development of a SSAMS might build upon techniques and methods that are already in operation today.

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