Multiple people crossing the street of a busy intersection in a city



Navigating intersections poses risks even when pedestrians have the right of way. While measures like TLPI and other innovations show promise, their effectiveness is maximized when coupled with Leading Pedestrian Intervals (LPIs). These intervals, allowing pedestrians to start crossing 3-7 seconds before vehicle traffic, reduce pedestrian-vehicle crashes by 13%, according to the Federal Highway Administration.

However, it’s crucial to consider the needs of visually impaired pedestrians. Accessible Pedestrian Signals (APS) provide vital audible and tactile cues, but their absence during LPIs can pose challenges for visually impaired individuals, resulting in lost time during the walk cycle.

In this exploration of pedestrian safety, we delve into the essential combination of LPIs and APS, addressing diverse pedestrian needs. We also examine key factors influencing LPI and APS implementation, from crash history to intersection visibility, and the calculations determining optimal LPI durations. Join us as we uncover strategies for safer intersections.


What is a Leading Pedestrian Interval?

While one might assume that merely having a pedestrian walk sign is sufficient to ensure safety during street crossings, the reality is often different. Instances of conflicts between vehicles and pedestrians, even when pedestrians have the legal right of way, are common—especially during turns, be it left or right. Various measures, such as blank-out signs preventing right turns, raised crosswalks, well-lit crosswalks, or innovations like PedSafety’s TLPI (Turn Lane Pedestrian Indicator), can be implemented by agencies to mitigate these conflicts. While these solutions are commendable on their own, their effectiveness can be significantly enhanced when accompanied by a Leading Pedestrian Interval (LPI).

As defined by the Federal Highway Administration, an LPI “gives pedestrians the opportunity to enter the crosswalk at an intersection 3-7 seconds before vehicles are given a green indication. Pedestrians can better establish their presence in the crosswalk before vehicles have priority to turn right or left”. According to the Manual on Uniform Traffic Control Devices (MUTCD), an LPI “should be at least 3 seconds in duration and should be timed to allow pedestrians to cross at least one lane of traffic or, in the case of a large corner radius, to travel far enough for pedestrians to establish their position before the turning traffic is released.”

The Federal Highway Administration reports that LPIs can reduce pedestrian-vehicle crashes at intersections by 13%. This reduction is attributed to increased visibility of crossing pedestrians, fewer conflicts between pedestrians and vehicles, higher likelihood of motorists yielding to pedestrians, and overall improved safety, particularly for pedestrians who may take longer to initiate movement into the intersection.

Despite these notable benefits, it’s essential to acknowledge that LPIs may lead to increased conflicts for pedestrians with visual impairments if not accompanied by Accessible Pedestrian Signals.


Why APS should be paired with LPIs

We are aware of the advantages that Accessible Pedestrian Signal (APS) devices offer to visually impaired pedestrians. The combination of audible cues and tactile indications plays a crucial role in providing essential information to the visually impaired, signaling when it is safe to cross, and conveying important geographic messages. In the absence of APS, visually impaired individuals rely on alternative cues, such as listening to traffic movements or feeling the wind generated by passing vehicles, to determine the appropriate time to cross the street.

While the Manual on Uniform Traffic Control Devices (MUTCD) suggests considering APS during implementation, we advocate for their consistent incorporation. A Leading Pedestrian Interval (LPI) temporarily halts vehicle movement for the initial 3 to 7 seconds of the walk indication. Without an audible cue from an APS device during this period, visually impaired pedestrians are unaware that it is their turn to walk. Consequently, when vehicles start moving again, these pedestrians lose valuable 3 to 7 seconds of the walk cycle and are no longer within the driver’s line of sight.

Even at intersections employing pedestrian recall and contemplating the introduction of LPIs, we uphold the importance of implementing APS devices. Activation through calls may not be necessary to provide benefits to the visually impaired. Given that visually impaired pedestrians are not informed about intersections being in recall, an audible indication becomes essential for them to initiate crossing at the correct time.


Implementing LPIs

When deciding when to incorporate Accessible Pedestrian Signals (APS) with Leading Pedestrian Intervals (LPI), various factors can guide the identification of intersections that would benefit the most from these implementations. These factors include:

  • Crash History
  • Pedestrian Crossing Volumes
  • Vulnerable Populations
  • One-Way Streets or T-intersections
  • Intersection Visibility

It is common to pair the implementation of an LPI with restricting Right Turns on Red (RTOR). This measure enhances pedestrian safety by recognizing that drivers during a right turn on red are often focused on oncoming traffic rather than observing the pedestrian crossing.

When determining the implementation details of an LPI, researchers have devised formulas to calculate the optimal duration. These formulas take into account the minimum time required for pedestrians to cross the first travel lane or reach the midpoint in one direction of travel. Larger crossings necessitate longer LPI durations, and in certain instances, extended LPIs may be required to minimize conflicts with left-turning vehicles.



The symbiotic relationship between Leading Pedestrian Intervals (LPIs) and Accessible Pedestrian Signals (APS) stands out as a key safety measure. LPIs, granting pedestrians a 3-7 second lead, resulting in a significant reduction in pedestrian-vehicle crashes. Despite LPI benefits, our exploration emphasizes the crucial role of APS for visually impaired pedestrians. The absence of APS during LPIs poses challenges, highlighting the necessity of consistent incorporation. Additionally, advocating for APS in intersections considering LPIs and pedestrian recall is vital. The absence of an audible cue during the initial LPI phase leaves visually impaired pedestrians unaware, emphasizing the need for APS devices.

By implementing LPIs and APS, factors like crash history, pedestrian volumes, vulnerable populations, and intersection visibility guide decisions are positively affected. Coupling LPI with restricting Right Turns on Red (RTOR) reflects a practical approach to address driver focus during right turns. Taking everything into account, in our pursuit of safer intersections, prioritizing the efficiency of LPIs and the inclusivity of APS devices creates a path to a safer, more accessible future.