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Creating Safe andCreating Safe and Efficient Traffic Flow:Efficient Traffic Flow:
GDOT I-285GDOT I-285 Increased Speed Limit and Increased Speed Limit and Variable Speed Limits Project Variable Speed Limits Project
Agenda
• Project Background
• Action Plan
• What are VSLs?
• Why is it needed?
• How it will work
• Discussion and Questions
Project Background
Project location: I-285
●Project Goals:oIncrease speed limit to 65 mph during non-
congested timesoProvide consistent travel timesoReduce accidents (primary and secondary)oDecrease sudden stops by slowing traffic in
advance (reduce accordion effect)
Action Plan Action Plan • The general speed limit on I-285 will be raised from
55 mph 65 mph.• The north side of I-285, (above I-20) is being
transitioned to variable speed limits (VSL). o The speed limit will be adjustable between 65
mph and 35 mph, depending on road conditions, o Expectation that the speed limit will remain at 65
mph the majority of the time.o Speed limit will be adjusted at 10 mph
increments.• The southern portion of I-285 (below I-20) will have
the speed limit raised permanently to 65 mph.
This color signifies the portion of I-285 that will undergo the change to VSLs from 35 mph up to the new increased speed limit of 65 mph
This color signifies the portion of I-285 that will permanently change to a 65 mph speed limit
What are Variable Speed What are Variable Speed Limits (VSLs)?Limits (VSLs)?
●VSL systems are a type of Intelligent Transportation System (ITS) that utilize current traffic speed and volume detection, weather information, and road surface condition technology to determine appropriate speeds for safe travel.
●VSL systems are usually part of a larger incident management, congestion management, weather advisory, or motorist warning system.
Why is it needed?• Traffic studies of I-285 have shown that an
increased speed limit is warranted. • Northern half of I-285 much more congested;
– carrying significantly more traffic each day than the southern half
– an average of 50,000 more vehicles and in some sections as many as 100,000 more.
• There also are more interchanges on the northern section (28) than the southern (15). – more weaving and more merging for drivers – Both increase the risk of accidents
Why is it needed?• Higher traffic volumes on northern section
of I-285 – traffic flow often deteriorates into a constant
accelerating/braking process – very inefficient and dangerous
• Studies show that by travelling at a slower but more consistent speed– eliminates accordion-like, stop-and-go pace, – Motorist save on gasoline, – Arrive at their destinations sooner
How it will work:● Posted speed will be based on current speeds measured
by roadway sensors (max 65 mph; min is 35 mph)● Posted speeds will be updated automatically via
NaviGAtor II (NAVII)oLogic will include:
– When to increase the speed– When to decrease speeds– How often speeds can change
● TMC can also override to manage the VSLs as conditions warranto Incidentso Eventso Weather
How it will work:● VSL signs are regulatory and
enforceable● Overhead dynamic message signs
will advise motorists in advance of an upcoming reduction in the speed limit
● Motorists will be advised of the reason for the speed limit change
● An array of LED speed limit signs will replace static signs on the outside shoulder and center median
Next StepsKey element to the future success
●EducationoWeb pageoVideo oInformation meetingsoLetters to stakeholdersoMedia relations
●Enforcement
These will lead to greater driver understanding and compliance.
1960 – Michigan – Congestion Mitigation
1960’s (late) – New Jersey – Congestion Mitigation
1989 – New Mexico – Congestion Mitigation
1995 – Colorado – Tunnel Truck Speeds
1998 – Arizona – Experimental – Weather Conditions
More recent:● I-270/I-255 Missouri – Congestion Mitigation (2008)● I-4 Orlando – Congestion Mitigation (2010)● “Smarter Highways” Washington – Congestion Mitigation
(2010)● United Kingdom – Congestion Mitigation (2006)
Brief history of VSLs
Questions?
