Flexing AI: Effect of Roundabout on Frederica and Sea Island Rd Traffic
Yesterday we hosted a successful Tech Tuesday workshop on AI at the Golden Isles Olive Oil Store. One of the items covered in the workshop was how to leverage the Deep Research feature of ChatGPT to help answer the question of how much of an improvement on driving time to the north end of the Island from Harris Teeter we should expect to see after the roundabout is installed. Enjoy the following report:
Input question to Deep Research in ChatGPT:
The drive to the north end of St Simons is getting worse and worse. We know that there's a roundabout planned for the intersection of Frederica and Sea Island roads. But we don't know exactly how much this will improve traffic. Based on all the info on the web published about this particular roundabout and also based on the improvements that other communities have experienced, project the before and after driving time from this intersection to Christ Church.
ChatGPT follow up questions before executing the Deep Research request:
To give you an accurate projection of the driving time improvements from the Frederica Road and Sea Island Road intersection to Christ Church on St. Simons Island, could you please confirm a few things:
What is the current average driving time (or your best estimate) from that intersection to Christ Church during peak hours?
Are there particular times of day or days of the week that are especially problematic?
Should I look at similar roundabout implementations in communities with similar traffic volumes, tourist activity, or geographic characteristics?
Is there a specific timeline for when the roundabout is expected to be completed?
This will help tailor the comparison and projection as closely as possible to your situation.
Our workshop response to these questions:
1. 20 minutes
2. Monday thru Friday from 1130 to 1
3. Yes
4. It keeps changing, not sure
Projected Impact of Frederica/Sea Island Roundabout on Drive Time to Christ Church
Current Traffic Conditions at Frederica & Sea Island Intersection
The intersection of Frederica Road and Sea Island Road on St. Simons Island is currently a notorious bottleneck. It handles very heavy traffic volumes – on the order of tens of thousands of vehicles per day, comparable to the busy Torras Causeway (which carries ~20,000 vehicles daily)thecurrentga.org. County officials have identified this junction as “one of the worst traffic intersections in Glynn County,” with daily congestion affecting thousands of residents and visitorsthecurrentga.org. During peak mid-day hours (around 11:30 AM to 1:00 PM on weekdays), drivers report that the drive from this intersection up to Christ Church (near Fort Frederica) can take roughly 20 minutes – a significant delay for a trip of only about 4–5 miles. This sluggish travel time is largely due to traffic backups and stops at the Frederica/Sea Island intersection, which currently uses a traffic signal to manage the heavy cross-traffic. Each red light cycle and stop-and-go queue contributes to the extended trip duration.
Planned Roundabout and Expected Benefits
A modern roundabout is slated to replace the signalized intersection at Frederica and Sea Island Road, with the goal of improving traffic flow and reducing these delays. According to Glynn County’s project summary, the roundabout is specifically designed to “reduce congestion and improve transitions” between Frederica Rd. and Sea Island Rd.glynncounty.org. By allowing continuous yielding flow (instead of full stops at a red light or stop sign), roundabouts let more vehicles pass through in the same amount of time. The county’s traffic analysis (including counts during peak tourist season) confirmed that a roundabout will yield “significant long-term benefits, improving traffic flow and safety through the design year 2041.”glynncounty.org In short, the new roundabout is expected to streamline traffic at this choke point, which should directly shorten travel times for trips heading north toward Christ Church.
In addition to easing congestion, the roundabout brings safety and other benefits. Its design will minimize conflict points (reducing severe crash types) and improve overall safety for motorists and pedestriansglynncounty.org. Continuous traffic flow also means less idling, which cuts vehicle emissions – a bonus for environmental qualitystories.opengov.com. These advantages align with community concerns about traffic delays hurting quality of life, and the project has been years in the making to address St. Simons’ growth and traffic woesglynncounty.orgthecurrentga.org.
Traffic Flow Improvements Seen with Roundabouts Elsewhere
Experience from other communities and studies of similar projects show that replacing a stop-or-signal intersection with a roundabout almost always improves travel times. Some key findings on roundabout benefits include:
Reduced Vehicle Delays: Research by the Insurance Institute for Highway Safety found that converting traditional intersections to roundabouts can cut vehicle delays by an estimated 62% – 74% on averageiihs.org. In some cases (e.g. when a heavily congested signal or four-way stop is replaced), delays have been observed to drop by as much as ~89%wsdot.wa.gov. Even more conservative studies (Kansas State University, for example) report roughly a 20% average reduction in delays after roundabout installationwsdot.wa.gov. The clear trend is that traffic spends far less time waiting.
Shorter Queues & Fewer Stops: With yield-at-entry, vehicles keep moving whenever gaps allow. Studies noted up to a 56% reduction in the number of stops vehicles had to make after roundabouts were installedwsdot.wa.gov. Shorter queues mean drivers spend less time creeping along or sitting at a standstill.
Higher Intersection Throughput: Because traffic isn’t halted by a red light cycle, a roundabout can handle more cars per hour than a comparable signal. The Washington State DOT explains that vehicles “don’t have to wait for a green light... so the intersection can handle more traffic in the same amount of time.” This continuous flow often translates into tangible travel time savings for driverswsdot.wa.gov.
These improvements have been borne out in various communities (for example, Carmel, IN saw dramatic drops in engine idling and quicker travel through intersections after building over 100 roundabouts). In summary, modern roundabouts consistently decrease overall travel times and delays, especially during peak traffic periods, by eliminating the long waits at red lights or stop signswsdot.wa.goviihs.org.
Projected Before-and-After Driving Time to Christ Church
Given the above, we can project how the mid-day drive from the Frederica/Sea Island intersection to Christ Church might improve once the roundabout is in place:
Before (Current Situation): Around 20 minutes on weekdays during the 11:30am–1:00pm period (as observed currently). This prolonged time is due to significant congestion and waiting at the intersection’s traffic light, where backups commonly occur.
After (With Roundabout): It is reasonable to expect a substantial drop in travel time. Even a conservative improvement (say, ~20% reduction in delay) would trim several minutes off the trip – roughly bringing it down to about 16 minutes instead of 20wsdot.wa.gov. However, the improvements could be much more pronounced. If the roundabout eliminates most of the idle time and long queues (as similar projects have achieved), the drive could be nearly cut in half. Studies showing ~60% less delay suggest the same route might only take on the order of 10–12 minutes in similar midday trafficiihs.org. In practical terms, local officials anticipate smoother flow and have aimed to “reduce traffic and increase safety for the thousands… impacted on a daily basis”thecurrentga.org – which implies drivers will spend far less time in line.
In summary, a reasonable projection is that the 20-minute lunchtime trip could drop to roughly 10–15 minutes once the roundabout is operational. The exact outcome will depend on traffic growth and driver familiarity with the roundabout, but double-digit percentage improvements in travel time are expected. The roundabout’s ability to keep cars moving with only brief yielding should shave off many minutes from the Christ Church drive, greatly alleviating the frustration of the current stop-and-go congestionwsdot.wa.goviihs.org.
Sources:
Glynn County Government – Sea Island/Frederica Roundabout Project Overview glynncounty.orgglynncounty.org
The Current GA (Feb 2025) – Traffic concerns and volume at Frederica/Sea Island (Old Stables Corner) thecurrentga.orgthecurrentga.org
Insurance Institute for Highway Safety – Research on Roundabout Benefits iihs.org
Washington State DOT – Roundabouts FAQ (delay and throughput improvements) wsdot.wa.gov
