Lane Closure Analysis: How to Plan Safer, Less Disruptive Road Construction Closures

Whenever road infrastructure needs repair or improvement, lane closures — and sometimes full road closures — are essential to provide workers safe access to construction zones. Likewise, closures can be key to effective traffic management during special events or unexpected incidents. But lane closures also disrupt normal traffic flow, frequently leading to congestion and slowdowns along impacted corridors. 

These disruptions can ripple throughout the nearby road network as traffic reroutes, leading to atypical traffic patterns and higher than usual volumes on other roadways that may not be equipped to accommodate them. On top of that, queuing around work zones can lead to end-of-queue crashes, while atypical traffic patterns on nearby roads may also lead to unsafe traffic conditions. 

In this article, we explore how you can improve road construction planning with lane closure analysis and real-time traffic monitoring before, during, and after active closures to minimize disruptions, ensure lane closures and detours are working as intended, and inform future planning of road construction.

What is a lane closure analysis?

A lane closure analysis helps transportation planners and traffic operations teams understand how a potential lane or road closure will impact road users, including drivers, road workers, and vulnerable road users.  

For example, as part of a lane closure analysis, agencies often investigate the potential impacts of a partial or total road closure on traffic congestion, travel times, routing behaviors, and work zone safety. 

Combining historical traffic insights and real-time road closure data is key to analyzing the potential impacts of lane closures and ensuring current closures are performing as intended. For example, agencies may want to confirm that closure-related travel delays are not resulting in a poor Level of Service (LOS), or that queues or speeding behaviors are not creating dangerous conditions for road workers. 

Put simply, a data-driven lane closure analysis helps agencies learn from historical traffic patterns to answer questions like: 

• How many lanes can I close without stalling traffic? 
• What time windows are best for a lane or road closure? 
• How will traffic spill over onto nearby streets during the proposed closure? Can those streets handle increased traffic? 
• What detour route(s) is best to keep traffic flowing smoothly and safely? 

Key components of lane closure analysis

There are a variety of traffic metrics that agencies commonly use to evaluate potential lane closures and design traffic management plans for road construction. Below, we explore some of the most commonly used metrics for lane closure analysis and how agencies can get access to them.

Vehicle volumes and roadway capacity

The more vehicles there are on the road, the more congested traffic becomes, leading to travel time delays and queuing patterns at bottleneck locations (e.g., in front of a work zone). 

Conversely, low traffic volumes can lead to excess capacity that results in higher traffic speeds, potentially creating dangerous conditions for road workers. Though lane closures typically reduce road capacity, monitoring speeding behaviors near work zones may be relevant during times when vehicle volumes typically drop below peak levels. 

For both these reasons, agencies need to understand how many vehicles will likely be on the road during the proposed closure and how that compares to a road’s capacity during the closure. 

Vehicle volumes can vary significantly over time, so having access to granular vehicle volume data is key. Instead of using a snapshot of vehicle volumes collected during a short time frame, look for volume data that allows you to compare traffic patterns during different hours of the day, weekdays vs. weekend days, and different months of the year. 

Vehicle speeds and other safety metrics 

As mentioned above, atypical vehicle speeds (both high and low) can lead to traffic management challenges during a lane closure. While atypically low speeds can signal congested traffic that may lead to travel delays and queuing, high speeds can be dangerous, especially for workers in an active work zone. 

Measuring historical speeds along the corridor where a lane closure is planned is critical to establish a baseline that can be used to help predict likely speeds during the proposed lane closure, as well as establish a baseline against which atypical speeds measured during a closure can be compared, informing how operations teams understand the severity of congestion or risk to safety. 

Queuing analysis for road closure 

When vehicles get backed up ahead of a bottleneck, leading to a line of vehicles that is significantly slowed or stopped, this is called queuing. Queueing can lead to major travel delays as well as dangerous stop-and-go traffic conditions. 

End-of-queue crashes are a particular risk during queued conditions, as faster-moving traffic suddenly encounters a line of slower-moving vehicles. These types of crashes can be particularly severe due to high speed differentials between the approaching and slowed/stopped vehicles. These crashes can also be difficult for responders to resolve because they may impact multiple vehicles at once during a time when access to the location where the crash occurred is already restricted by an active closure and congested traffic conditions. 

Reviewing real queuing patterns from historical closures can help agencies implement effective road construction safety plans that reduce the risk of end-of-queue crashes. Similarly, agencies can use data on historical vehicle and truck volumes and speeds to help predict where queues are likely to form during a lane closure, how long they may get, and how much they may impact travel times. 

Additionally, monitoring real-time queuing during an active closure can help traffic operators deliver timely information to drivers, keep work zones safe, and implement congestion mitigation measures if needed. For example, operations teams may use queue warning systems to alert drivers to slowdowns, which can give drivers opportunities to reroute around bottlenecks and reduce their risk of crashing into slower-moving vehicles. 

Getting the data you need for lane closure analysis 

Traditional traffic data collection methods like sensors, cameras, and manual counts can be used to gather metrics needed for a lane closure analysis, such as vehicle volumes and speeds. However, these methods may offer limited spatial or temporal coverage, while manual counts can also put staff at risk. 

Traffic management software powered by big data analytics can help fill in coverage gaps while offering highly granular insights into both historical and real-time driving patterns, helping agencies design and implement effective road construction traffic management plans.  

StreetLight’s Traffic Monitor product helps streamline lane closure analysis with historical and real-time insights into vehicle volumes, speeds, queuing behaviors, and incidents. Agencies can use the product’s Closure Impacts module to forecast how specific lane closure plans may impact congestion, travel times, and spillover traffic. Additionally, Traffic Monitor’s Queuing module can help agencies monitor real-time queuing patterns as they emerge, enabling effective traffic management and rapid response measures when needed. 

Agencies have also used StreetLight’s Connected Vehicle Data to measure and monitor queuing around work zones. We’ll touch on that more on that use case below.

Data in action: How to get answers to common traffic operations questions

So how exactly can agencies use the data they collect to actually plan effective lane closures that minimize traffic disruptions and keep people and vehicles moving safely? 

In this section, we explore how to get data-supported answers to common questions planners and operators ask when designing and implementing lane or road closures. 

Question 1: When is the best time to close a lane for construction? 

The timing of a lane closure is key to ensuring work zone safety and protecting project timelines while also minimizing impacts to the traveling public. Closures during peak travel hours could lead to the largest delays and spillover traffic. But what about a weekend closure? Or a midday closure that avoids the morning and evening rush hours? 

Agencies can use historical vehicle volume data during typical conditions – or during past closures, if available – to understand how vehicle activity compares to available road capacity to understand how severely a lane closure could impact congestion and travel times. 

One way agencies can easily compare different lane closure time windows is by using Traffic Monitor’s Volumes and Closure Impacts modules. The Volumes module allows users to understand how volumes shift in 15 minute increments over the course of the day, while the Closure Impacts module allows users to set up and compare different closure scenarios using different time windows, as well as weekday vs. weekend closure scenarios. 

Traffic Monitor can also be used to monitor real-time conditions during a closure to confirm if lane closure windows are functioning as intended. For example, when Caltrans used Traffic Monitor during a highway repaving project, they discovered that traffic conditions actually allowed for closure windows to be expanded, resulting in a shorter timeline to completion.

Question 2: How will a lane closure impact traffic throughout the road network? 

Before approving a lane or road closure, agencies need to understand how the closure could impact traffic patterns on nearby roadways in addition to the corridor where the closure is planned. After all, traffic slowdowns on one corridor frequently have ripple effects throughout the road network as drivers reroute and backups spill over onto nearby ramps, access roads, or intersections. 

Analyzing historical routing and Origin-Destination patterns can help agencies anticipate where traffic is likely to reroute during a closure, informing detour planning and other traffic management measures. Engineers may also create a micro-simulation using metrics like these to help predict traffic impacts. 

Alternatively, agencies can use the Closure Impacts module in StreetLight’s Traffic Monitor product to quickly evaluate how different closure scenarios will likely impact traffic on nearby roadways. Users can easily compare how variables like number of lanes closed and the day and time of the closure affect spillover traffic. 

For example, in the demo video below, we explore different closure scenarios for a potential closure along I-81 in New York, using Traffic Monitor’s Closure Impacts module to compare three main scenarios: 1) a weekday single-lane closure from 9 a.m. to 3 p.m.; 2) a weekday two-lane closure from 9 a.m. to 3 p.m.; and 3) a weekend two-lane closure from 9 a.m. to 3 p.m. 

The analysis reveals that, based on how traffic volumes spill over onto nearby roads, a weekend two-lane closure may offer the best balance of minimizing traffic disruptions while speeding up the overall road work timeline. See how we did it:

Question 3: Is my lane closure plan working? 

Road conditions can change quickly and unexpected incidents or weather conditions may compound lane closure impacts for drivers or compromise safety for road workers. That’s why it’s important for traffic operations teams to stay on top of current traffic conditions so they can spot incidents, help resolve queues, and mitigate slowdowns if needed. 

To do so, agencies need access to real-time or near-real-time insights on travel times, queue length, delays, and road incidents. Traditional methods of traffic monitoring often include the use of sensors and field observations by agency staff, as well as monitoring public complaints. 

These methods do have some drawbacks though, including limited coverage and lag time, which can impact how quickly issues are discovered and resolved. 

StreetLight’s Traffic Monitor includes tools like a Real-Time Incident Feed and Queuing module to help alert operators to emerging issues and evaluate whether they require intervention. 

Agencies have also used StreetLight’s connected vehicle data (CVD) to spot queues in real time and feed timely information to automated queue warning systems during active road construction. Check out the video below to see how Iowa is using CVD to monitor queuing around work zones.

Question 4: Based on past closures, what can I adjust for the future? 

Lane closure analysis doesn’t stop after lanes are reopened. Reviewing what happened to traffic during the closure is an important tool to improve future closures and develop repeatable playbooks that traffic operations teams can use when implementing future planned or emergency lane closures. 

Access to historical data from before, during, and after the lane closure is key for agencies to evaluate the success of their traffic management plans, spotting where lane closure windows could be expanded, shifted, or reduced; where bottlenecks caused queued traffic, and what measures could help mitigate disruptions in the future. Useful metrics include changes in speeds, travel times, traffic volumes, and queue durations. 

In the video below, we show how agencies can use Traffic Monitor to review past closures and inform future closure planning.

Common lane closure analysis challenges

The effectiveness of a lane closure analysis is highly dependent on the quality of the data that goes into it. Agencies need validated, granular, and full-coverage data sources to help reliably forecast how proposed lane closures could impact traffic and monitor performance in real time. 

There are several common challenges agencies often face in gathering the data needed for effective lane closure planning, including: 

• Limited coverage of physical sensors: Whether it’s permanent sensors or temporary counters installed along the roadway, physical sensors can only gather data at the exact locations and times that they are operational along a corridor. This can make it difficult to evaluate potential detouring and spillover traffic, as well as conditions that may form upstream or downstream from a sensor’s location. This is particularly challenging when it comes to monitoring traffic on new roads or ramps and adjacent roadways that may not already have counters installed. 

• Dangers to staff: When staff are sent to install temporary sensors, perform manual counts, or monitor current conditions, they face potentially dangerous traffic conditions. 

• Outdated datasets: In many cases, agencies may only have access to historical data from several years ago when counts were last taken on a specific corridor. This old data may not reflect changes to travel demand, land use, and road design that can significantly impact how traffic changes during a lane closure. 

• Data lags: During an active closure, having up-to-date data is key to resolve issues quickly. Public complaints and incident reports may help alert traffic operations teams to disruptions, but often these indicators only come in minutes or hours after conditions have begun to deteriorate, prolonging disruptions and exacerbating their impacts. 

How StreetLight enhances lane closure analysis for effective road construction planning 

As explored above, agencies need reliable, timely, and full-coverage data to design effective traffic management plans for road construction. That’s why many agencies use StreetLight to fill data gaps and conduct lane closure analyses that can help forecast likely traffic impacts. 

StreetLight offers the deepest and most comprehensive repository of transportation data available on the marketplace, helping agencies leverage historical and real-time traffic data to address their top challenges. 

StreetLight’s Traffic Monitor product is specifically tailored to address common planning and traffic management challenges that impact daily traffic operations, road construction scenarios, special event planning, incident response, evacuation planning, and more. You can learn more about big data–powered operations in our Traffic Operations Toolkit. 

Agencies also use StreetLight’s connected vehicle data to gain real-time insights into work zone safety and traffic queues to help monitor lane closure performance and enable timely communication with the traveling public. 

To see if StreetLight can help you optimize your next lane closure, reach out to our team today.