There are numerous improvements that are part of the plan for vehicular safety.
The reversible lane has been identified by DDOT as a safety hazard to road users of all types going back to studies in the early 2000's. DDOT's existing conditions report (link here, pages 13 and 14) indicates that very few of motorists actually were using the two outside lanes (the reversible and the curbside lane), with approximately 2/3 of traffic leveraging the two interior lanes throughout the corridor.
Despite this low utilization, the amount of traffic accidents occurring in the corridor disproportionately happened when the reversible lanes were in effect. About 44% of traffic accidents occurred when the reversible lanes were open - which were only open 15% of the time! Removal of the reversible lanes is expected to have a large decrease in the amount of accidents, which when they occur can snarl traffic for the entire corridor.
In lieu of the reversible lanes, there will now be dedicated left hand and right hand turn support for the most heavily used intersections with turning activity (e.g., Porter Street for example). This will shift turning traffic out of the travel lane, enabling traffic to continue to flow without north/south-bound drivers needing to filter from behind a turning vehicle into the other moving lane.
This too is expected to have a big downward effect on traffic accidents. 27% of accidents were a left hand turning vehicle hitting another vehicle when trying to turn across flowing traffic. 24 were side-swipes from lane changes. By allowing for dedicated turn support, the need to shift travel lanes constantly throughout the corridor to avoid backups is reduced.
While those vehicle commuters who use the entirety of Conn Avenue on their commute will see some increases in their total trip duration (expected to increase from about 13-15 minutes to 20-23 minutes), they also only accounted for about 20% of total Conn Avenue road users in the Existing Conditions report (see page 27-28 here).
For those users who leverage some of Conn Avenue, travel times may increase slightly, but the ease of use of the Avenue should also be increased via the roadway simplification & intersection improvements for turning traffic. Thus the majority of road users will see a modest increase in travel time, but should have a more predictable experience of driving the Avenue with lower accidents and lane changes being required.
Importantly, DDOT's projections for the traffic impact do not include estimates of the demand-preference switch for alternative transportation options and the impact those additional options would have on residual vehicular volume (see video below on Induced Demand for more).
A deep dive on traffic statistics before and after the addition of bike lanes & traffic calming from various NYC infrastructure investments.
Vehicular-based travel follows a concept called "induced demand". Learn more about this concept here.