FAA’S IMPLEMENTATION OF RUNWAY 

STATUS LIGHTS 

Federal Aviation Administration 

Report Number: AV-2008-021 

Date Issued: January 14, 2008 
U.S. Department of 

Memorandum

Transportation 

Office of the Secretary 

of Transportation 

Office of Inspector General 

Subject: ACTION: FAA’s Implementation of Runway 

Status Lights 

Date: January 14, 2008 

Federal Aviation Administration 

Report Number AV-2008-021 

From: David A. Dobbs 

Principal Assistant Inspector General 

 for Auditing and Evaluation 

Reply to 

Attn. of: JA-1 

To: Acting Federal Aviation Administrator 

This report provides the results of our review of the Federal Aviation 

Administration’s (FAA) implementation of Runway Status Lights (RWSL). We 

conducted this review as part of our ongoing efforts to assess FAA’s actions to 

reduce runway incursions. The objectives of our audit were to (1) determine 

RWSL’s viability for reducing runway incursions and (2) assess FAA’s progress 

in implementing the system. Our review was conducted between June and 

January of 2008 and included site visits to Dallas/Fort Worth International Airport 

(DFW) and FAA Headquarters. Exhibit A details our scope and methodology. 

BACKGROUND 

Most runway incursions (potential collisions on a runway) are caused by a lack of 

situational awareness, and over half of all runway incursions are the result of pilot 

deviations. However, there is currently no automated technology in place to 

directly warn pilots of potential runway conflicts. Reducing runway incursions 

has been on the National Transportation Safety Board’s (NTSB) Most Wanted List 

of Safety Improvements since the list’s inception in 1990. However, NTSB 

considers FAA’s response to this safety improvement to be unacceptable because 

it has not yet implemented a technology that gives immediate warnings of 

probable runway incursions directly to flight crews in the cockpit. 

During our recent audit of FAA’s efforts to reduce runway incursions, we met 

with a safety team from the Air Line Pilots Association, International (ALPA) to 

discuss runway incursion mitigation. ALPA officials told us that RWSL, a 
2

technology that FAA is evaluating, could be an effective tool for reducing runway 

incursions. 

RWSL was first developed and demonstrated at Boston Logan International 

Airport in the early 1990s, but the surveillance systems available at that time 

needed improvements before the technology could be viable. In 2003, a prototype 

system was installed at DFW. A second prototype system was also installed at 

San Diego International Airport in 2005. Testing of these systems continues at 

both locations. 

What Is RWSL? 

RWSL technology uses automated, surveillance-driven lights that work as an 

independent, direct warning system to alert pilots in departing or crossing aircraft 

that the runway is occupied. The lights are installed at runway/taxiway 

intersections and at departure points along the runways. Lights illuminate red 

when it is unsafe to cross or depart from a runway, thus serving to increase the 

crew’s situational awareness and decrease the potential for a runway incursion. 

What Are Its Components? 

RWSL consists of both runway entrance lights and take-off hold lights. Runway 

entrance lights illuminate red when a runway is unsafe to enter or cross (see 

figure 1). Runway entrance lights are visible to aircraft from taxiways holding 

short of runway intersections. 

Figure 1. Diagram of Entrance Lights Figure 2. OIG Photo of Entrance 

Lights at DFW 

Runway entrance 

lights

Runway 18L 

The audit team observed DFW runway entrance lights illuminate red on taxiway B 

when runway 18L was unsafe to enter due to an aircraft taking off (see figure 2). 
3

Take-off hold lights illuminate red to indicate an unsafe condition when an aircraft 

is in position for take-off and another aircraft or vehicle is either on or about to 

enter the runway in front of it (see figure 3). Take-off hold lights are visible from 

the take-off hold position. 

Figure 3. Diagram of Take-Off Hold Lights 

Figure 4. OIG Photo of Take-Off Hold 

Lights at DFW The audit team observed take-off 

hold lights illuminate red on runway 

18L at DFW when the runway was 

unsafe to depart due to an aircraft 

crossing the runway in the distance 

(see figure 4). Aircraft crossing 

the runway 

Take-off hold 

lights FAA is also developing a third type 

of runway status lights, runway 

intersection lights. These lights are 

designed to warn pilots on a runway 

when another aircraft is departing 

from or landing on an intersecting 

runway. FAA plans to begin testing 

these lights at Chicago O’Hare 

International Airport in 2008. 

What Drives the System? 

RWSL is driven by fused multi-sensor surveillance system information. Using 

Airport Surface Detection Equipment-Model X (ASDE-X), external surveillance 

information is taken from three sources that provide position and other 

information for aircraft and vehicles on or near the airport surface. RWSL safety 

logic processes the surveillance information and commands the field lighting 

system to turn the runway status lights on and off in accordance with the motion of 

the detected traffic. The diagram of RWSL below (figure 5) depicts the use of 
4

three sources of surveillance input to provide position of aircraft and vehicles on 

the airport surface. 

Figure 5. Diagram of RWSL Surveillance Sources

At DFW, RWSL uses input from the ASDE-X prototype system, which uses three 

sources of surveillance: (1) Terminal Radar—Airport Surveillance Radar (ASR), 

(2) Airport Surface Radar—Airport Surface Detection Equipment-Model 3 

(ASDE-3), and (3) Transponder Multilateration System. 

RESULTS IN BRIEF 

We found that RWSL is a viable technology for preventing runway incursions. 

While FAA has made progress in developing RWSL, this technology is still in the 

early stages of implementation; much work remains for FAA to achieve full 

deployment. Essential attributes of RWSL include the following: 

• Timely warnings of potential conflicts—RWSL promptly and clearly indicates 

to pilots and vehicle operators when it is unsafe for aircraft to enter or cross a 

runway or to commence take-off. 

• Automated information—RWSL provides this information at all times without 

human input. 

• No interference with Air Traffic operations—RWSL acts as an independent 

safety enhancement. It does not increase controller workload and does not 
5

interfere with the normal flow of airport traffic or rhythm of controller 

movement of traffic. 

• Lights indicate status only—RWSL indicates runway status and does not 

convey an Air Traffic Control clearance. Clearance is still provided by Air 

Traffic Control. 

• Illuminated lights warn pilots of potential runway conflicts and prompt them to 

notify the tower before proceeding if a contradicting clearance has been issued; 

therefore, the system may also help to identify potential controller operational 

errors. 

During operational evaluations and subsequent modifications at DFW for runway 

entrance lights and take-off hold lights, RWSL met or exceeded all performance 

criteria specified in the RWSL Research Management Plan. In addition, all 

system users we met with at DFW agreed that RWSL works as intended and has 

no known negative impact on capacity, communication, or safety. 

Further, runway incursions on the test runway at DFW (runway 18L/36R) have 

decreased by 70 percent: during the 29 months before testing (October 1, 2002, 

through February 28, 2005), 10 runway incursions occurred at DFW; during the 

29 months after testing (March 1, 2005, through July 31, 2007), only 3 occurred. 

While RWSL at DFW has performed extremely well thus far, we identified 

several challenges that FAA must address to ensure the effective and timely 

implementation of this important safety technology. For example, 

• RWSL depends on ASDE-X, and the interface between the two systems will 

need to be modified to address the differences between the ASDE-X prototype 

system used at DFW for RWSL and the version of ASDE-X being deployed 

nationally at other airports. 

• Some of the airports where FAA plans to deploy RWSL are undergoing or will 

undergo airfield improvements. It will be important for the RWSL program 

office to work with FAA’s Airports line of business to identify those airports 

and coordinate the deployment of RWSL in-ground infrastructure concurrently 

with airfield construction. This will help to save investment dollars by 

avoiding duplicative construction and ensure timely implementation of both 

infrastructure improvements and RWSL. 

• Part of the early success of RWSL testing has been immediate input and 

corrective actions taken by the research and development (R&D) staff 

(including the federally funded research contractor that created the system) 

when problems were identified. A key factor for maintaining project 
6

momentum will be ensuring that similar “hands-on” knowledge is retained 

during the transition from R&D to the acquisition phases of the RWSL life 

cycle. 

Meeting these challenges in the early phases of RWSL implementation will be 

critical for keeping it on track. 

FAA has made progress in developing RWSL thus far. FAA successfully 

conducted R&D and live operational testing at DFW, and FAA’s Joint Resource 

Council (JRC) approved the RWSL initial investment decision in July 2007. The 

initial investment decision document included recommendations that FAA finalize 

(definitize) its acquisition strategy and return it to the JRC for the final investment 

decision (which sets the stage for system-wide implementation) no later than 

November 2007. 

Obtaining approval from the JRC for the final investment decision is a key 

milestone because FAA cannot issue a contract for RWSL implementation until 

the program office obtains that approval. However, the target date for the final 

investment decision is currently set for July 2008. The RWSL program officials 

stated that the final investment decision milestone was established to provide 

sufficient time to prepare the acquisition package, which is required to award a 

contract. 

Expediting the RWSL acquisition is important since the JRC directed the program 

office, during the initial investment decision, to review alternatives to accelerate 

the RWSL deployment schedule. In our opinion, setting the target date for the 

final investment decision 1 year after the approval of the initial investment 

decision to complete the acquisition package does not meet that direction. 

Accordingly, we believe that the program office needs to expedite preparation of 

the acquisition package and establish a new target date for the final investment 

decision milestone to accelerate RWSL deployment. 

Our recommendations focus on the actions FAA needs to take now to ensure that 

the system remains a viable tool for reducing runway incursions and that future 

deployment remains on schedule. Our full recommendations are listed on page 13. 
7

FINDINGS 

We found that RWSL is a viable and important technology for reducing runway 

incursions and that FAA has made progress in developing it. RWSL has gained 

widespread support among user groups. Pilots, pilot union officials, Air Traffic 

management, and the airport operator at DFW all agreed that RWSL works as 

intended and has no known negative impact on capacity, communication, or 

safety. NTSB officials stated that RWSL is a promising technology for addressing 

its longstanding recommendation to provide direct warnings to pilots of potential 

runway conflicts. Further, the local National Air Traffic Controllers Association 

representative stated that RWSL has no impact on air traffic controllers’ duties and 

responsibilities. While RWSL is only one of many efforts to improve runway 

safety, FAA recognizes the need to expedite technologies that increase cockpit 

crews’ situational awareness and thus potentially reduce runway incursions. 

Several challenges need to be addressed, however, before the system can be 

effectively deployed. 

RWSL Is a Viable Technology for Reducing Runway Incursions 

RWSL promptly and clearly indicates to pilots and vehicle operators when it is 

unsafe for aircraft to enter or cross a runway or to commence take-off. RWSL 

provides this information automatically at all times without human input. As 

shown in figure 6, runway incursions have significantly decreased on the RWSL 

test runway at DFW—from 10 to 3 (70 percent) for the periods compared. 

Figure 6. Number of Runway Incursions at DFW’s 

Runway 18L/36R Where RWSL Is Installed 

0

2

4

6

8

10

12

29 Months Before

Start of Testing

(10/1/02 through

2/28/05)

29 Months After Start

of Testing (3/1/05

through 7/31/07)

Category D

Category C

* Runway incursions are graded by severity of the incident (A through D). 

Category A is the most severe, and Category D is the least severe.

 *

10

3

Source: OIG analysis of FAA data 

Of the three runway incursions that occurred after testing began, one was caused 

by a pilot, one by a vehicle operator, and one by a controller. 
8

We observed RWSL in operation at DFW from the vantage points of the airport 

surface and the control tower. We observed that RWSL acts as an independent 

safety enhancement. It does not increase controller workload and does not 

interfere with the normal flow of airport traffic or rhythm of controller movement 

of traffic. Further, RWSL only indicates runway status—it does not convey Air 

Traffic Control clearance to pilots. Clearance is still provided by Air Traffic 

Control. 

RWSL may provide additional safety benefits as it has shown the capability to 

prevent runway incursions caused by air traffic controllers (operational errors). In 

a documented example at DFW, RWSL prevented an operational error and a 

runway incursion. The error playback showed that the pilot of a taxiing aircraft 

questioned a runway crossing clearance given by the ground controller when 

runway status lights were illuminated red, indicating the runway was not clear. In 

response, the controller cancelled the runway crossing clearance and another 

aircraft’s landing clearance, thus avoiding both an operational error and a runway 

incursion. 

FAA Has Made Progress in Developing RWSL but Needs To Address 

Several Challenges To Effectively Deploy the System 

We found that FAA has made progress in developing RWSL thus far. During 

operational evaluations and subsequent modifications for runway entrance lights 

and take-off hold lights at DFW, RWSL met or exceeded performance criteria 

specified in the RWSL Research Management Plan. Most of the anomalies 

identified during initial tests have been mitigated. In addition, stakeholders and 

users at DFW reported that the FAA contractor was responsive to feedback and 

took quick and effective actions when system anomalies were identified. FAA 

successfully conducted R&D and live operational testing at DFW, and FAA’s 

Joint Resource Council approved the RWSL initial investment decision in July 

2007. 

RWSL appears to be a viable technology, and FAA is moving toward 

implementation; however, the Agency will need to address several challenges that 

may impede the timely and effective deployment of the system. These include: (1) 

modifying the interface between RWSL and ASDE-X to address the differences in 

the ASDE-X prototype system at DFW and ASDE-X systems being deployed at 

other airports, (2) coordinating with airports that are undergoing runway 

improvements and planning to deploy RWSL in-ground infrastructure 

concurrently with airfield construction, (3) ensuring that “hands-on” RWSL 

expertise is maintained during the transition from R&D to the acquisition phase; 

(4) equipping vehicles with transponders; and (5) mitigating delays in 

implementing ASDE-X. 
9

Modifying RWSL To Address Differences Between the ASDE-X Prototype 

System at DFW and the National ASDE-X System

Before RWSL can be deployed system-wide, FAA will need to modify RWSL to 

address differences between the ASDE-X prototype system at DFW and the 

ASDE-X system it is deploying at other airports. The ASDE-X system used to 

test RWSL at DFW was purchased by the Airport Authority in 2001 and is not 

part of FAA’s current, national ASDE-X program. The ASDE-X prototype 

system at DFW differs in that it does not include the fusion of ASDE-3 surface 

radar and ASR-9 approach radar. 

The national ASDE-X system has undergone additional changes since 2001. As a 

result, there are differences that could affect how RWSL software needs to be 

programmed so that it works as effectively at other locations as it has at DFW. 

For example, the ASDE-X prototype system at DFW has not received any of the 

hardware upgrades installed on the ASDE-X systems being deployed under the 

national program. 

We also found that the ASDE-X prototype fusion process at DFW for RWSL 

differs from the process used for the national ASDE-X system. This is the process 

that ASDE-X uses to estimate the location of aircraft and vehicles on the airport 

surface. It does this by gathering inputs from the three different surveillance 

mechanisms. For example, for RWSL, ground radar data are transmitted to the 

RWSL processor separate from other surveillance inputs. By doing so, RWSL has 

been able to operate effectively during rain because the RWSL safety logic is able 

to turn off radar data and use multilateration data (from local transponders) only, 

thus eliminating the impact of rain-induced radar clutter. However, the fusion 

process used by the national ASDE-X system fuses all three surveillance inputs 

into one data output. Consequently, an alternative method for filtering raininduced clutter will have to be implemented and tested to ensure continued reliable 

RWSL operation. FAA needs to modify RWSL software to address the 

differences between these systems during early RWSL implementation to limit 

risks of delays or impaired effectiveness. 

Coordinating With Airports To Deploy RWSL In-Ground Infrastructure 

Concurrently With Airfield Construction 

FAA will also need to coordinate with airports that are undergoing airfield 

construction to ensure that RWSL is installed concurrently to limit unnecessary 

construction efforts and costs. Although RWSL has progressed through the initial 

investment decision process, it is not yet a certified system. Therefore, airports 

cannot use FAA funds (i.e., grants from the Airport Improvement Program) for 

early installation of RWSL lighting. Nevertheless, several airports, including 

Los Angeles and Chicago O’Hare International Airports, have expressed interest 

in installing RWSL early and bearing some of the costs. 
10

Timing the installation of RWSL in-ground infrastructure is critical for these 

airports as they are both undergoing major runway construction projects. By 

installing RWSL sites during airfield construction, airports and FAA (after system 

certification) could save time and money. Lighting standards for RWSL have 

already been established, and site preparation for the lighting portion of RWSL 

could be initiated in advance. FAA is working with airport authorities at both Los 

Angeles and Chicago to determine if this is a feasible effort. 

The RWSL program office needs to work with FAA’s Airports line of business to 

identify other airports that are scheduled to receive RWSL and have ongoing or 

planned runway improvements. This is important to ensure that RWSL in-ground 

infrastructure is deployed concurrently with the airfield construction to avoid 

duplicative construction efforts and costs. 

Retaining RWSL Program Expertise When Transitioning From R&D to 

Acquisition 

At DFW, the airport operator, FAA management officials, and pilots praised the 

efforts of the FAA Surface Safety group and its contractor during R&D testing for 

RWSL. They also commended the group’s responsiveness and efficiency in site 

adaptation of the system. FAA’s Surface Safety group and its federally funded 

R&D contractor (MIT Lincoln Laboratory) have led the R&D process for RWSL 

since 2001 and are very familiar with the project. Mitigating individual site 

anomalies is vital to successfully implementing RWSL, and other planned sites 

could benefit from the “lessons learned” at DFW. 

FAA should take advantage of lessons learned during the past 5 years of the 

RWSL research and development phase at DFW. FAA’s own risk assessment 

indicated that the RWSL safety logic must be designed so that it can adapt to any 

airport. To address this issue, the risk assessment team recommended that FAA 

ensure that lessons learned during R&D be passed on to the software designer of 

RWSL. FAA needs to ensure that the RWSL acquisition program office benefits 

from the DFW group’s RWSL expertise. 

Equipping Vehicles With Transponders so They Can Be Detected by 

RWSL 

RWSL works with ASDE-X, which is designed to reduce the risks of ground 

collisions caused by vehicle operators by providing positive identification of 

vehicles operating on the airport surface. However, this safety feature will be 

limited unless airport vehicles are equipped with transponders. If airports equip 

their vehicles with transponders, they could reduce the risks of these types of 

runway incursions since RWSL could then track those movements under all 

conditions. 
11

In addition, during rain, RWSL safety logic filters out ground radar data and uses 

only multilateration, which requires a transponder. Without transponders, vehicles 

that enter a runway will not trigger the RWSL to “turn on”; therefore, pilots may 

not get the warning they need to avoid potential runway incursions caused by 

vehicle deviations. It is important for FAA to encourage airport officials to equip 

vehicles with transponders since about 16 percent of all runway incursions are 

caused by vehicle operators; these types of incursions can pose serious safety 

risks. 

In our October 2007 report on ASDE-X,1

 we recommended that FAA encourage 

airport officials to equip vehicles with transponders so that ASDE-X can provide 

positive identification of vehicles. Those actions are equally important for RWSL 

to work effectively. 

Mitigating Delays in FAA’s Master Schedule To Limit Adverse Impacts on 

RWSL Deployment 

RWSL operates with ASDE-X and cannot be commissioned at a specific airport 

until ASDE-X is commissioned at that airport. The initial investment decision for 

RWSL identifies 19 airports for planned RWSL implementation and includes a 

proposed deployment master schedule with November 2009 for the first 

operational site and March 2014 for the final site. 

FAA research and development officials told us that they built a 1-year buffer into 

FAA’s proposed RWSL waterfall to compensate for potential delays in the 

ASDE-X national deployment. The RWSL program office subsequently informed 

us that it plans to implement RWSL concurrently with the ASDE-X schedule to 

expedite RWSL deployment, completing all sites by the end of 2011. Therefore, it 

is imperative that ASDE-X remains on schedule since any delays in its 

implementation would trigger cascading delays in RWSL implementation. 

Our October report stated that FAA had not met its deadlines for installing 

ASDE–X equipment. During FY 2006, FAA only commissioned four of the seven 

planned ASDE-X systems. We reported that these schedule delays occurred 

because of FAA’s failure to establish a realistic master schedule through ASDE-X 

completion that outlines when all activities associated with commissioning each 

site for operational use will be completed. In response to our draft report, FAA 

provided us with an updated waterfall schedule. However, the schedule was 

incomplete and did not address the intent of our recommendation that system 

deployment should not be considered complete until all planned capabilities are 

fully tested and in place. We requested that FAA provide us with updated 

 

1

 OIG Report Number AV-2008-004, “FAA Needs To Improve ASDE-X Management Controls To Address Cost 

Growth, Schedule Delays, and Safety Risks,” October 31, 2007. OIG reports can be found on our website: 

www.dot.oig.gov. 
12

information regarding this issue. It will be important that FAA keep ASDE-X on 

schedule to avoid delays in both RWSL and ASDE-X implementation. 

Expediting RWSL Implementation 

FAA has made progress in developing RWSL thus far. FAA successfully 

conducted R&D and live operational testing at DFW, and FAA’s Joint Resource 

Council approved the RWSL initial investment decision in July 2007. The initial 

investment decision document included recommendations that FAA finalize 

(definitize) its acquisition strategy and return it to the JRC for the final investment 

decision (which sets the stage for system-wide implementation) no later than 

November 2007. 

Obtaining approval from the JRC for the final investment decision is a key 

milestone because FAA cannot issue a contract for RWSL implementation until 

the program office obtains that approval. However, the target date for the final 

investment decision is currently set for July 2008. The RWSL program officials 

stated that the final investment decision milestone was established to provide 

sufficient time to prepare the acquisition package, which is required to award a 

contract. 

Expediting the RWSL acquisition is important since the JRC directed the program 

office, during the initial investment decision, to review alternatives to accelerate 

the RWSL deployment schedule. In our opinion, setting the target date for the 

final investment decision 1 year after the approval of the initial investment 

decision to complete the acquisition package does not meet that direction. 

Accordingly, we believe that the program office needs to expedite preparation of 

the acquisition package and establish a new target date for the final investment 

decision milestone in order to accelerate RWSL deployment. 

There is also significant congressional support for expediting RWSL deployment. 

In the FY 2008 House Appropriations Bill,2

 the Committee provided $20 million 

for RWSL, an increase of $14.7 million over the budget request. 

 

2

 H. Rep. No. 110-238, “Departments of Transportation and Housing and Urban Development and Related Agencies 

Appropriations Bill, 2008,” (July 18, 2007). 
13

RECOMMENDATIONS 

To limit any potential risks that could impact the successful and timely 

implementation of RWSL, we recommend that FAA: 

1. Modify the RWSL software design to address the differences between the 

ASDE-X prototype system used at DFW for RWSL and the national 

ASDE-X system being deployed at other airports. 

2. Ensure that the RWSL program office (a) coordinates with FAA’s Airports 

line of business to identify locations that are scheduled to receive RWSL and 

have ongoing or planned runway improvements and (b) secures agreements 

with those airports to deploy RWSL in-ground infrastructure concurrently 

with airfield construction to avoid duplicative construction efforts and costs. 

3. Ensure that existing RWSL program expertise is retained during the system’s 

transition from R&D to the acquisition phase to capitalize on lessons learned 

at DFW in addressing system and site-specific anomalies. 

4. Expedite preparation of the acquisition package to make the final investment 

decision earlier than the current July 2008 milestone to accelerate RWSL 

deployment as directed by Congress and the JRC. 

AGENCY COMMENTS AND OFFICE OF INSPECTOR GENERAL 

RESPONSE 

We provided FAA with a draft of this report on November 20, 2007, and received 

FAA’s reply on December 20, 2007. FAA concurred with each of our 

recommendations and provided appropriate planned actions and target dates. 

• Recommendation 1: FAA stated that the RWSL program office is developing 

the requirements for the needed ASDE-X interfaces and will implement the 

software by September 30, 2009. 

• Recommendation 2: FAA stated that the RWSL program office is in the 

process of coordinating with the Airports line of business and is working 

towards securing agreements with specific airports by September 30, 2008. 

• Recommendation 3: FAA stated that the RWSL program office has been 

coordinating with the R&D office and MIT Lincoln Laboratory to create a 

transition plan and ensure an efficient transfer of technology and lessons 

learned. FAA stated that these actions will be completed by March 31, 2008. 
14

• Recommendation 4: FAA stated that the RWSL program office is exploring 

different options to expedite the acquisition and will issue a Request for Offer 

by February 2008. 

FAA also provided several general comments, such as referring to the ASDE-X 

system at DFW as a prototype system. We incorporated FAA’s suggested changes 

as appropriate. FAA’s response is included in the appendix to this report. 

ACTIONS REQUIRED 

FAA’s response and planned actions address the intent of our recommendations. 

Therefore, we consider these recommendations resolved. 

We appreciate the courtesies and cooperation of FAA representatives during this 

audit. If you have any questions concerning this report, please contact Lou Dixon 

Assistant Inspector General for Aviation and Special Program Audits, at 

(202) 366-0500 or Dan Raville, Program Director, at (202) 366-1405. 

# 

cc: FAA Acting Deputy Administrator 

Anthony Williams, ABU-100 
15

EXHIBIT A. SCOPE AND METHODOLOGY 

We conducted this performance audit in accordance with generally accepted 

Government Auditing Standards prescribed by the Comptroller General of the 

United States. As required by those standards, we obtained evidence that we 

believe provides a reasonable basis for our findings and conclusions based on our 

audit objectives. We conducted this review between June 2007 and November 

2007 using the following methodology. 

To evaluate the viability of RWSL and FAA’s progress in implementing this 

technology, we: 

• reviewed RWSL research and development documents, including operational 

concept, operational evaluation (live testing) reports, pilot survey results, and 

the research management plan. 

• interviewed FAA Air Traffic Organization officials from the Technology 

Development—Surface Systems Group; Financial Services, Capital 

Expenditures—F&E Requirements NAS Baseline Management Group; and 

FAA Airport Safety and Standards representatives. 

• conducted a site visit to DFW airport where RWSL is being tested and 

observed RWSL in operation from the air traffic tower and airport surface. 

• interviewed DFW’s local FAA Air Traffic Management officials, National Air 

Traffic Controllers Association representative, airport operator, airline pilot 

union and safety officials (Allied Pilots Association and ALPA), and 

contractor representatives from MIT Lincoln Laboratory. 

• met with ALPA headquarters officials to discuss their concerns. 

We did not rely on information contained in data bases maintained by the Agency 

as part of this review. Therefore we did not conduct a data reliability assessment. 

Exhibit A. Scope and Methodology 
16

EXHIBIT B. MAJOR CONTRIBUTORS TO THIS REPORT 

THE FOLLOWING INDIVIDUALS CONTRIBUTED TO THIS REPORT.

Daniel Raville Program Director 

Mary (Liz) Hanson Project Manager 

Annie Glenn Bungo Senior Analyst 

Benjamin Huddle Analyst 

Tasha Thomas Analyst 

Andrea Nossaman Writer-Editor 

Exhibit B. Major Contributors to This Report 
17

APPENDIX. AGENCY COMMENTS 

Federal Aviation 

Administration 

Memorandum 

Date: December 20, 2007 

To: Robin Hunt, Acting Assistant Inspector General for Aviation and Special 

Program Audits 

From: Ramesh K. Punwani, Assistant Administrator for Financial Services/CFO 

Prepared by: Anthony Williams, x79000 

Subject: OIG Draft Report: FAA’s Implementation of Runway Status Lights (RWSL) 

Federal Aviation Administration 

Thank you for providing us the opportunity to review and comment on your draft report 

entitled: “FAA’s Implementation of Runway Status Lights Federal Aviation Administration”, 

dated November 20. 

Below is the agency’s response to each of the recommendations cited in your report. While 

the FAA concurs with all the recommendations, we are of the opinion that various areas of the 

report will require additional clarification before the final report is released. Following the 

response to the recommendations, we have provided comments addressing our concerns to 

statements made in the body of the report. 

Recommendation 1. Modify RWSL software design to address the differences between the 

ASDE-X system used at DFW for RWSL and the national ASDE-X system that FAA is 

deploying at other airports. 

FAA Response: Concur. The RWSL program office is developing the requirements 

governing the interfaces to the Airport Surface Detection Equipment Model X (ASDE-X) as 

part of the RWSL acquisition process. The specification will state that the RWSL processor 

shall receive surveillance, status, and operational configuration data from the ASDE-X 

system in accordance with the latest version of the ASDE-X Interface Description Document. 

The RSWL software will be implemented by September 30, 2009. 

Appendix. Agency Comments 
18

Recommendation 2. Ensure that the RWSL program office (a) coordinates with FAA’s 

Airports line of business to identify locations that are scheduled to receive RWSL and have 

ongoing or planned runway improvements and (b) secures agreements with those airports to 

deploy RWSL in-ground infrastructure concurrently with airfield construction to avoid 

duplicative construction efforts and costs. 

FAA Response: Concur. The RWSL program office is coordinating with the Airports line 

of business and also plans to secure agreements with airports. The RWSL program office, 

based on the availability of funding and the alignment of schedules, will pursue concurrent 

airfield construction where possible. Planning dates will be coordinated with airfield 

construction dates. We anticipate this to occur by September 30, 2008. 

Recommendation 3. Ensure that existing RWSL program expertise is retained during the 

system’s transition from R&D to acquisition phase to capitalize on lessons learned at DFW in 

addressing system and site-specific anomalies. 

FAA Response: Concur. The RWSL program office has been coordinating with the R&D 

offices. Several meetings have been held to gain a better understanding of the R&D 

activities, not only concerning the prototype RWSL system at Dallas/Ft. Worth, but also 

future R&D technology development activities related to runway incursions. As a result of 

these meetings a transition plan is being developed by the R&D office to ensure an efficient 

transfer of technology and lessons learned. The RWSL program office has also had meetings 

with Lincoln Laboratories, the developer of the prototype system software, to discuss the 

system, as well as lessons learned. RWSL program office personnel went to Dallas/Ft. Worth 

to view the prototype system and meet with individuals at the airport involved in the RWSL 

prototype operation. Meetings have been held with the R&D office, Lincoln Laboratories, 

and other functional organizations to further discuss and execute the technology transfer. 

Action will be considered complete in 2Q, FY08 (March 31, 2008) when the program office 

funds Lincoln Laboratories for technical support. 

Recommendation 4. Expedite preparation of the acquisition package to make the final 

investment decision earlier than the current July 2008 milestone to accelerate RWSL 

deployment as directed by Congress and the JRC. 

FAA Response: The FAA concurs with this recommendation and has been exploring 

different acquisition strategies for the acceleration of the schedule. RWSL Request for Offer 

(RFO) release is scheduled for February 2008. 

Note: FAA’s response also included minor general comments (e.g., suggested wording 

changes) that did not have any bearing on our report’s findings and recommendations. We 

incorporated these suggestions as appropriate but did not include them in the appendix. 

Appendix. Agency Comments 
The following page contains textual versions of the graphs and charts found in this 

document. This page was not in the original document but has been added here to 

accommodate assistive technology. 
FAA’s Implementation of Runway Status Lights (RWSL) 

508 Compliant Presentation 

Figure 1. Diagram of Entrance Lights 

Diagram shows aircraft stopped at hold line by red lights. This alerts the pilot to wait 

until runway is clear before entering. 

Figure 2. OIG Photo of Runway Entrance Lights 

At Dallas-Forth Worth International Airport, the audit team observed illuminated 

runway entrance lights signaling that an intersecting runway, Runway 18L, was not 

clear for entrance due to a departing aircraft on the runway. 

Figure 3. Diagram of Take-Off Hold Lights 

Diagram shows take-off hold lights illuminating red to alert a pilot waiting to take off 

that another aircraft or vehicle is either on or about to enter the runway in front of the 

aircraft. 

Figure 4. OIG Photo of Take-Off Hold Lights 

At Dallas-Forth Worth International Airport, the audit team observed take-off hold 

lights illuminate red on runway 18L. This alerted the pilot awaiting take-off that the 

runway was unsafe to depart due to an aircraft crossing the runway in the distance. 

Figure 5. Diagram of RWSL Surveillance Sources 

The diagram shows RWSL in use at an airport. It depicts the use of three sources of 

surveillance input to provide position of aircraft and vehicles on the airport surface so 

that the light technology can operate. The three sources depicted are: airport surface 

radar, transponder multilateration, and approach radar. 

Figure 6. Number of Runway Incursions at Dallas-Forth Worth International 

Airport, Runway 18L/36R Where RWSL Is Installed (Note: Runway incursions 

are graded by severity of the incident [A through D]. Category A is the most severe, 

and Category D is the least severe.) 

In the 29 months before RWSL testing started at Dallas-Fort Worth International 

Airport (October 1, 2002 through February 28, 2005), there were 10 runway 

incursions. Four of these were Category C incidents, and six were Category D 

incidents. In the 29 months after RWSL testing started at Dallas-Fort Worth 

International Airport (March 1, 2005 through July 31, 2007), there were three runway 

incursions. All three incursions were Category D incidents (least severe category).