Ask Dr. Delay: Tricky exits on I-275

At Exit 20 of I-275 in St. Petersburg, northbound traffic bears to the left to leave the interstate rather than on the far right.

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At Exit 20 of I-275 in St. Petersburg, northbound traffic bears to the left to leave the interstate rather than on the far right.

Reader Joseph Gehrig asked the Doc to look into what he considers to be a safety problem on northbound Interstate 275 at Exit 20, which is the 31st Street S exit. This is a bit of an unusual exit in that northbound traffic bears to the left to leave the interstate rather than the more common far-right lane exits.

Gehrig says that judging by the skid marks and damage to the guardrail adjacent to the exit, he can only imagine the number of crashes that might take place there. The problem, as Gehrig sees it, is that the approach to the exit does not provide adequate warning to motorists that the far left lanes are exit lanes. So some drivers may be unaware that they have in fact left the interstate until the road curves sharply before it intersects with 31st Street S, which is where the guardrail damage can be seen.

Kris Carson of the Florida Department of Transportation disagreed with Gehrig's assessment that motorists don't have adequate advance warning that the two left lanes of northbound I-275 are exit-only lanes prior to Exit 20. And, Carson said, several traffic control devices intended to provide for safe operation and speed reduction on this off-ramp are provided by the DOT to include speed limit signs, two signs that warn of a stop ahead, and several sets of thermoplastic rumble strips that meet state standards. There are also two signs that warn of the curve ahead and continuously flashing yellow lights at the intersection.

"We can't however, regulate the behavior of drivers who do not slow down accordingly based on these traffic control devices. In the future we do plan to install EXIT followed by ONLY pavement messages in the left lanes on approach to this exit in support of the overhead EXIT ONLY guide signs," Carson added.

Merge if you dare

We've had reader inquiries about northbound I-275 farther up the road, this time at 38th Avenue N, specifically the on ramps. The issue is the acceleration lane, which feeds traffic into two consecutive exit-only lanes for 54th Avenue N. This makes for some treacherous maneuvering, unless, as one reader put it, "You're lucky enough to find another motorist willing to let you migrate over two lanes at high speed just to get into the flow."

Some readers have asserted that the problem is the extra left lane that appears in I-275 just north of 22nd Avenue N. "If the interstate were restriped to painlessly funnel drivers into that new lane and other drivers to in essence shift one lane over, much of this hazard could likely be mitigated, allowing a safer merge," one reader suggested.

Kevin Dunn of the DOT's traffic operations office broke it down for us:

Northbound I-275 has three through lanes that continue after the 22nd Avenue N exit to the 38th Avenue N exit. The northbound on-ramp from 38th Avenue N merges into the right through-lane, which then ends as an exit-only drop lane to the 54th Avenue N exit. An additional exit lane is added to the right side of the road before the 54th Avenue N exit in order to provide both the eastbound and westbound 54th Avenue N exits with a dedicated lane.

"That is the primary reason (for the) left lane adds in this area in order to provide the additional lane of through capacity to compensate for the right lane ending at the 54th Avenue N exit," Dunn wrote in an email, noting that motorists are informed well in advance of the exit to 54th Avenue N that the right lane is an exit-only lane, allowing for plenty of time to perform a lane-change maneuver. But it doesn't always happen that smoothly. Throw in some visitors unfamiliar with the road or a timid driver trying to navigate in rush-hour traffic and it gets pretty dodgy.

Dunn said that usually when pavement is added, as is the case with the creation of the left lane that provides four northbound lanes between 38th Avenue N and 54th Avenue N, designers don't re-stripe other sections of the pavement, such as the far-right lane that drops at 54th Avenue N.

Email DocDelay@gmail.com with traffic concerns. Follow Dr. Delay on Twitter @AskDrDelay. Questions may be edited for space or clarity.

Ask Dr. Delay: Tricky exits on I-275 03/31/12 [Last modified: Saturday, March 31, 2012 3:52pm]

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