As a follow-up to some comments or questions over the past few months:
Signal timing is one of the biggest issues any transportation organization faces. Optimally, we would like to give every one using the roadway a green light just as they need it. Realistically, with the volumes and necessity to meet the needs for all roadway users (including transit, bikes and pedestrians), that cannot happen. The best any department can do is to balance the timing along a corridor – trying to ensure that all users get their fair piece of available green time. That means that the roadway with the most traffic should be the one that gets the most green time. Unfortunately, several arterials carry large amounts of traffic east and west, or north and south, and usually cross. The corridor is balanced (or optimized) to provide as much seamless progression along the corridor as possible for a vehicle traveling the posted speed limit.
Ideally, a major traffic corridor has a certain ebb and flow to it, or “pattern.” The goal for engineers is to move traffic into the corridor from side streets with a minimal delay for the overall, safe flow of traffic along the corridor. When you add roads with high numbers of vehicles (such as an interstate or a major crossroad), that creates breaks in the corridor’s ebb and flow. It is often more efficient, when looking at the overall corridor movement, for traffic engineers to do what they can to incorporate those major roadways into the corridor’s existing flow. That may mean stopping traffic near that major roadway on either side to get them into the corridor’s “pattern.”
The challenge is when you have two major roadways that intersect – especially if one is an interstate. You see the biggest concerns at the I-44 or I-64 ramps at roadways such as Jefferson, Kingshighway, Hampton or any other major city artery. The first priority is clearing the interstate ramp – you do not want the traffic backing all the way up onto the interstate and backing up traffic there – it’s just not safe. But, when you have an interchange with a major road, you want to minimize the backups on that major roadway as well. Traffic engineers have to find the balance on both roads -- and consider the overall traffic flow at not only the interchange, but the corridor. For instance, in the morning at I-44 and Jefferson, engineers have to balance the volume of traffic on both the eastbound ramp with the traffic heading north on Jefferson coming from Russell. Lafayette and Russell remain green to clear traffic out of the way for the ramp traffic. Once the eastbound I-44 ramp traffic enters Jefferson headed north, it passes the westbound ramp and some traffic gets stopped at the Lafayette signal to get into the “pattern” for the Jefferson corridor. If the signals are “synched” at the ramps, Lafayette and Russell, then traffic may flow worse further along the corridor.
This is complicated by several items:
• Many of the signals along corridors are older equipment
• Several signals along the corridor don’t have pedestrian buttons (which means that engineers must give time every cycle to possible pedestrians (even if there is nobody there)
• Signals are owned and operated by two different organizations with two different signal control systems.
Our engineers work diligently with the city to keep the major corridors (such as Kingshighway, Hampton, Chouteau, Jefferson, Chippewa and Gravois) flowing consistently and smoothly. Andrew Gates, MoDOT Communications
Thank you for your patience and understanding.
Last week there was a post about River Desperes and Landsdowne. City Traffic has adjusted the detection at this intersection and is awaiting new equipment to install. We will continue to monitor this intersection.
City Traffic staff will observe and adjust timing at this intersection.
We will inform out Street Dept. crews and repair.
City Traffic staff are in the process of re-designing the traffic signal patterns and lane configuration.
The City will contact our vehicle enforcement staff.
The St. Louis County Police Department enforces this section of Barrett Station Road, and its patrol officers are alert for the illegal u-turning motorists. However, I'll forward your observations to them. Thank you for your posts. (Your earlier comment prompted the study that led to the installation of the "No U-Turn" signs. David Wrone, St. Louis County
Martha, MoDOT has responsibility for the 20th Street and Chestnut ramps from I-64. At this time, we have no funding planned for any work at 20th and Chestnut. Andrew Gates, MoDOT Communications
The pots/traffic circles are currently being removed in ward 25 & replaced with stop signs until a more permanent, safe, & engineered solution can be implemented.
Marianne -- Typically a resurfacing job such as the one recently completed on Clarkson does not include the shoulders. We make repairs to the driving lanes that are necessary due to the constant vehicle traffic. Potholes are an annual occurance, especially in the spring, and would not be prevented by resurfacing work. If we put a new surface on the shoulders (which isn't normally needed) we would still have to patch potholes. Andrew Gates, MoDOT Communications
Good morning!Bringing up a previous topic/location: at the intersection of Des Peres Road & the offramp from WB Manchester/Corporate Hill Drive, the new stoplight arrangement... Nothing has been done to give more time to those of us trying to exit the Corporate Hill Campus (literally HUNDREDS of cars). There is still only time enough for four (maybe five, if the first car out is "on" the gas when the light goes green) to get out of the parking lot. The timing is horrible.Also, since last week, at the SAME intersection - the offramp from WB Manchester now has a dual-left onto Des Peres Road, but there are no "tiger tracks" in the intersection to keep cars in their own lanes.Finally: Why are traffic lights that control traffic from a State Highway onto a City Street allowed to be controlled by a commercial property developer???
We will pass this on to the team working on the project. Typically, when you have a major permit job such as this that requires significant changes and equipment to a state roadway, we require the contractor/developer to maintain the roadway and the signals they are impacting. That way, we are not making changes that are interfering with their work and vice versa (and taxpayers aren’t on the hook if the contractor is not fixing potholes or the like) . In situations such as this, one of the requirements for the contractor is a traffic engineer who is able to make changes to signals. When the project is done, and we believe the roadway is back to an acceptable condition, we take maintenance responsibility back. We do something similar when we have major construction on one of our roadways (our contractor is responsible for the road’s condition while they are working on it.). Andrew Gates, MoDOT Communications
Sorry, meant to respond to this one earlier. Closing the right lane would reduce the safety of the drivers entering or exiting the interstate (it would require much shorter merges at the entrance and exit ramps. ) Andrew Gates, MoDOT Communications
The City Traffic staff will address these locations.