Appropriate Actions May Be Necessary To Prepare Traffic Signals For The New Changes To Daylight Savings Time

Changes to Daylight Savings Time may Impact Traffic Signal Operation

The results of a brief survey have shown that only a small percentage of agencies that operate and maintain traffic signals have taken action to prepare traffic signals for the changes to Daylight Savings Time (DST) that take effect this year.

The 2005 Energy Policy Act has extended DST by one month. Previously DST took effect for most of the United States at 2 a.m. on the first Sunday of April and reverted to standard time at 2 a.m. on the last Sunday of October. Beginning this year DST begins for most of the United States at 2 a.m. on the second Sunday in March (March 11^th) and reverts back to standard time at 2 a.m. on the First Sunday of November (November 4^th).

If no action is taken traffic signal controllers may have incorrect time settings from March 11^th - April 1^st and October 28^th - November 4^th; resulting in Time of Day signal timing plans being offset by one hour on the dates indicated. Peak hour timing plans offset by one hour could potentially increase traffic delays at signalized intersections. It is recommended that this information be passed along to state and local agencies involved in the operation or maintenance of traffic signals to encourage appropriate action to be taken.

Agencies should be advised to check their system documentation to determine how these changes will effect the operation of their system(s). One or more of the following actions may be necessary:

Controllers with Programmable DST Settings

Update the settings to reflect the new implementation dates prior to March 11^th. Verify that the changes take effect and monitor the operation of the system particularly on the dates of March 11, April 1, October 28 and November 4, 2007.

Controllers without Programmable DST Settings Connected to a Central System or External Time Source

Contact controller manufacture for availability of firmware or software update; install update prior to March 11^th. If firmware or software update is not available; disable DLS feature on controller and implement time update from central system or external time source. If DST feature cannot be disabled; implement time update from central on March 11^th and verify time settings on April 1^st, October 28^th and November 4^th.

Controllers without Programmable DST Settings not Connected to a Central System or External Time Source

Contact controller manufacture for availability of firmware or software update; install update prior to March 11^th. If firmware or software update is not available; disable DST feature on controller and implement time update manually on March 11^th. If DLST feature cannot be disabled; implement time update manually on March 11^th and again on April 1^st, October 28^th and November 4^th.

For further information, please contact Eddie.Curtis@dot.gov.

Search Operations: Arterial Management Home FOCUS AREAS Traffic Signal Management Traffic Signal Operations & Maintenance Signal Timing Access Management PRACTITIONER TOOLBOX Awareness/Outreach Publications Training & Workshops ACS-Lite Traffic Analysis Tools RESOURCES Arterial Management Team FHWA Resource Center Operations Team Links Contact Us	Appropriate Actions May Be Necessary To Prepare Traffic Signals For The New Changes To Daylight Savings Time Arterial Management Home > Traffic Signal Timing Changes to Daylight Savings Time may Impact Traffic Signal Operation The results of a brief survey have shown that only a small percentage of agencies that operate and maintain traffic signals have taken action to prepare traffic signals for the changes to Daylight Savings Time (DST) that take effect this year. The 2005 Energy Policy Act has extended DST by one month. Previously DST took effect for most of the United States at 2 a.m. on the first Sunday of April and reverted to standard time at 2 a.m. on the last Sunday of October. Beginning this year DST begins for most of the United States at 2 a.m. on the second Sunday in March (March 11^th) and reverts back to standard time at 2 a.m. on the First Sunday of November (November 4^th). If no action is taken traffic signal controllers may have incorrect time settings from March 11^th - April 1^st and October 28^th - November 4^th; resulting in Time of Day signal timing plans being offset by one hour on the dates indicated. Peak hour timing plans offset by one hour could potentially increase traffic delays at signalized intersections. It is recommended that this information be passed along to state and local agencies involved in the operation or maintenance of traffic signals to encourage appropriate action to be taken. Agencies should be advised to check their system documentation to determine how these changes will effect the operation of their system(s). One or more of the following actions may be necessary: Controllers with Programmable DST Settings Update the settings to reflect the new implementation dates prior to March 11^th. Verify that the changes take effect and monitor the operation of the system particularly on the dates of March 11, April 1, October 28 and November 4, 2007. Controllers without Programmable DST Settings Connected to a Central System or External Time Source Contact controller manufacture for availability of firmware or software update; install update prior to March 11^th. If firmware or software update is not available; disable DLS feature on controller and implement time update from central system or external time source. If DST feature cannot be disabled; implement time update from central on March 11^th and verify time settings on April 1^st, October 28^th and November 4^th. Controllers without Programmable DST Settings not Connected to a Central System or External Time Source Contact controller manufacture for availability of firmware or software update; install update prior to March 11^th. If firmware or software update is not available; disable DST feature on controller and implement time update manually on March 11^th. If DLST feature cannot be disabled; implement time update manually on March 11^th and again on April 1^st, October 28^th and November 4^th. For further information, please contact Eddie.Curtis@dot.gov.
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