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91 CHAPTER 8 CONCLUSIONS AND RECOMMENDATIONS CONCLUSIONS The research has shown that: ⢠The distance at which drivers can detect objects in reality falls significantly short of the headlight SD calculations used in determining the design of sag vertical curves. ⢠Neither changing the length of the curve, the deceleration rate, nor the design speed would be sufficient for increasing the headlight SD. ⢠The only way to increase headlight SD in order to match SSD would be enhancements to the headlamps or the addition of other vision enhancement systems to supplement the headlamps. RECOMMENDATIONS Based on these conclusions, no recommendation for changes to the AASHTO design policy is being proposed at this time. Rather, it is recommended that a significant review of the current values of safe SSDs and headlamp performance be considered to align the performance requirements of the driver and the performance delivered by the headlamps system. This review may include the consideration of the potential changes in the SSD as discussed in this report or changes in headlamp requirements.
