Traffic!
Anyone who finds themselves traveling North on Roxboro Street during the afternoon rush hour knows how congested it is with existing traffic. The same is true for other roads near the planned development, such as the intersection of Guess and Horton Roads.
These are major commuter corridors that are already overburdened and under-equipped, even before Northern High School is added into the mix. Northern High School will have over 1500 students, adding more traffic on Roxboro and nearby roads, with much of it in the morning during peak rush-hour. Think about this as you drive past the Northern site, which is now under construction.

A Traffic Impact Analysis for the Westpoint project was published in 2019 (Download a copy here). That analysis used data from December 2018 and did not account for the new high school. A new cumulative traffic assessment is needed to take into account the cumulative impact of both of these projects that will be constructed simultaneously near the same N. Roxboro St. intersections.
It appears that the study claims no new traffic light would be required. Drivers attempting to turn left from the development onto Roxboro Street, will need a great deal of skill and more than a little luck to succeed with this during rush hour given the very heavy traffic. The additional congestion will also contribute to the difficulties city buses and school buses have in stopping along N. Roxboro and other area streets, given that the roads in Northern Durham are not equipped with bus pull-off areas.
The proposed development would also encourage impatient drivers stuck in heavy traffic on N. Roxboro to cut through the development over to Stadium Drive, causing a heavy flow of traffic speeding through small neighborhood streets. Given the lack of any pedestrian sidewalks on Roxboro St and most area neighborhood streets, the additional traffic load will further exacerbate existing pedestrian and cycling safety problems that have already resulted in injuries and deaths.