Problems and Causes
Access to and from the Queen Anne neighborhood through the Halladay Street intersection is problematic, especially in the p.m. peak period. Although the posted speed limit is 40 miles per hour, northbound SR 99 N. traffic often travels in excess of 50 miles per hour approaching this intersection. Vehicles exiting SR 99 N. slow and often queue in the outside through lane. This queuing takes place on a curved section of roadway, which limits sight distance. The combination of slow moving vehicles, limited sight distance with a horizontal curve, and approaching vehicles traveling at 40 miles per hour or faster creates a potentially hazardous situation. This situation has a high potential for rear-end accidents.
Vehicles entering SR 99 N. northbound from Halladay Street are also a concern. Currently, vehicles have no acceleration lane at the Halladay Street entrance to SR 99 North. So vehicles must directly enter the outside through lane that immediately narrows to 9.5 feet in width. This movement is also on a curve and involves high-speed traffic. This presents a high potential for rear-end and entering-at-angle accidents associated with this movement.
Options Considered
To address the accidents at Halladay Street, four alternatives were considered: converting the outside lane to a drop/add lane, adding a new acceleration lane, adding a new deceleration lane, and installing new signage. The option of converting the northbound outside lane to a drop/add lane was proposed to separate exiting and entering vehicles from the through traffic. This alternative would require all through traffic to merge into the left two lanes south of the intersection and remain there until a midpoint on the Aurora Bridge. With the exception of the p.m. peak period, this would create a new choke point by requiring all through traffic to operate in two lanes instead of three. The queuing associated with this conversion would create the potential for more rear-end accidents on northbound SR 99 North. This option was removed from consideration because of the adverse impacts it would have on traffic congestion and safety.
A second option was to add a northbound acceleration lane for vehicles accessing SR 99 N. from Halladay Street. This modification would require additional right-of-way and necessitate constructing a new structure to connect to the Aurora Bridge. The additional right-of-way and new bridge structure are needed to provide adequate acceleration room and taper distance for vehicles to merge into the outside through lane. The right-of-way would have significant impacts on the Canlis Restaurant that has been identified as an historic building. Because of the right-of-way impacts and cost associated with a new structure, this option was eliminated. New road signs were also considered to address the problems in this area. Signs warning of slowing, exiting, or entering vehicles are possible, but would not likely have a dramatic impact on the accident or congestion problems in this area. This option was not considered solely sufficient to address the back-ups and accidents occurring at the Halladay exit. However, this option was considered complementary to other intersection and channelization improvement options and is included in the study's final recommendations.
Recommendation
The final improvement recommendation for this area was to add a new outside deceleration lane approaching Halladay Street and to relocate Halladay Street to the south. See Figure 6-3. This option would allow vehicles to be removed from the through traffic before slowing to exit. Another benefit of this option would be the increased distance between the Canlis restaurant driveway and the Halladay Street intersection. There would be right-of-way impacts associated with this alternative as additional width on the east side of SR 99 N. is necessary to add a new lane and shift Halladay Street to the south.
This set of options was recommended; however, it would be a long-term solution as property redevelopment would likely be necessary to obtain the needed right-of-way. As part of this recommendation, new signs warning of slowing, exiting, or entering vehicles to the Queen Anne Drive/Halladay Street intersection are recommended.
back to top