To Lead or be Exclusive... for Pedestrians at a Traffic Signal

 A fellow APBP member asked the following question: a topic that keeps coming up is the idea of using exclusive pedestrian phases versus other measures to improve pedestrian safety.  I've seen mixed messages on this as an outcome, including the possibility that exclusive phases may have fewer, but more serious collisions, or that pedestrians won't wait for the phase to come up, or that it might not be significant relative to LPI's blank out signage, etc.  On the other hand, it is a relatively simple thing to implement assuming it doesn't result in operational challenges for other modes (admittedly a large assumption in many cases).

Is there anything definitive available for documentation, or at least something that helps with a decision-making process?

My answer:

This is a topic that I have been fortunate to have reviewed a good amount of work from some really smart researchers. Sirisha Kothuri or Portland State, David Hurwitz of Oregon State, Ed Smaglik of Northern Arizona University to name a few. These folks have collaborated on this topic for awhile, but the conclusions on efficiency are pretty similar in every study. Generally, the efficiency from a multimodal perspective is better with LPIs as compared to Exclusive Pedestrian Phasing. The safety issues are much more site dependent and in my opinion difficult to assess. 

Efficiency

Improving Walkability Through Control Strategies at Signalized Intersections by Kothuri, et al

Shorter version in the ITE Journal here 

"The results of the simulations show that the addition of an exclusive pedestrian phase significantly increased delay across the modes when compared to the base case for all pedestrian volume scenarios. These results are intuitive as the addition of an exclusive pedestrian phase increases cycle length, which results in increased delay for all modes."

The Oregon DOT has a nice write up summarizing literature review on LPIs here and Peter Furth of Northeastern University has also done some wonderful research on this topic.

Safety

Of course, delay for all modes isn't the only metric one would consider as you pointed out. FHWA cites the potential for reduced crashes for both strategies as an LPI as 0.413 and that of an Exclusive Ped Phase as 0.49, meaning that there is (1-0.49) 51% reduction in pedestrian crashes is expected for this countermeasure in the Toolbox of Pedestrian Countermeasures and Their Potential Effectiveness

A study of pedestrian compliance with traffic signals for exclusive and concurrent phasing by Ivan, John etal 

"We found that pedestrian compliance is significantly higher at intersections with concurrent pedestrian phasing than at those with exclusive pedestrian phasing, but this difference is not significant when compliance at exclusive phase intersections is evaluated as if it had concurrent phasing. This suggests that pedestrians treat exclusive phase intersections as though they have concurrent phasing, rendering the safety benefits of exclusive pedestrian phasing elusive." 

The paper goes on... 

"This is very important since, as Abrams and Smith (1977) pointed out back in 1977, the safety benefit of exclusive pedestrian phases over concurrent pedestrian phases depends entirely on pedestrian compliance." 

I would caution you about the perspective that it is "relatively simple thing to implement" given potential legal liabilities of accessibility issues at a signalized intersection. This case in Chicago was one that is worth learning more about.