SafeCurves

SafeCurves categorizes curves into Class 1, 2 or 3 depending on whether they are: 

• unacceptable (Class 1)

• undesirable (Class 2)  

• desirable (Class 3)

• uncategorized (Class 4)

The design limit is determined by the combination of the approach speed, and the curve radius. For example, a tight radii curve can be desirable if drivers approach it at a low speed, or unacceptable if drivers approach it at high speed.   

The ‘undesirable’ and ‘unacceptable’ design limits are considered out-of-context, with ‘unacceptable’ being more out-of-context than ‘undesirable’.   

SafeCurves: Identify has been applied to all high-speed ≥40mph roads in the USA covering approximately 213,000 miles of roads and identifying over 1,725,000 horizontal curves.   

The outputs have been validated against data contained in the National Highway Traffic Safety Administration (NHSTA) Fatality Analysis Reporting System (FARS).   

While only 2% of the network was classified as ‘unacceptable’ curves, this category of highway had the highest average number of fatal crashes. The fatal crash rate on ‘unacceptable’ curves is 1.4 times that of ‘desirable’ curves and 2.1 times that of straights. This suggests that ‘undesirable’ and ‘unacceptable’ curves are high-risk curves. The implication is that targeting interventions at high-risk curves will yield greater road safety benefits and provide a greater return on investment. 

SafeCurves is provided via an access key so that you can either use the SafeCurves App on your desktop or mobile device and via your preferred GIS platform, or you can access the data as a GDB.

The data is supplied in perpetuity.  At the conclusion of the Plan term there is an opportunity to renew, and the data is updated to the current methodology version.