Recommended Guidelines for Nighttime Overhead Sign Visibility

Abstract

Guidelines for the provision of effective nighttime performance of overhead signs were developed. Relevant policies and guidelines with regard to sign lighting currently provide little useful information to determine when sign lighting is needed, and the reference material available to practitioners is out of date. Two complementary nighttime visibility studies were conducted, which were designed to produce results useful in developing updated guidelines for overhead sign visibility. The first was conducted on a closed course and investigated the legibility distances of three sign legend and background configurations under various sign lighting treatments. The second was conducted on the open road. It investigated the effects of sign luminance and visual complexity on the distance at which a driver can read overhead signs during a recognition task. The combined findings were used to develop revised guidelines designed to provide adequate nighttime visibility of overhead signs. The proposed guidelines are based on the needs of nighttime motorists and have been formatted specifically for AASHTO’s Roadway Lighting Design Guide, which is being updated. The revised chapter on roadway sign lighting was provided to the AASHTO task force responsible for revisions. The guidelines include a list of recommended retroreflective sheeting materials that can be used to meet nighttime driver needs for specific complexity levels.

Improving Autonomous Vehicle Perception through Evaluating LiDAR Capabilities and Handheld Retroreflectivity Assessments

“…Other studies have also explored the complex relationship between environmental variables and retroreflective attributes within traffic signs, including contamination, precipitation, temperature, and relative humidity; refs. [ 1 , 7 , 8 ] have contributed insights into the installation chronology, orientation, geographical disposition, color, and classification of traffic signs, all of which can impact road sign retroreflectivity.…”

Traffic Signs Conspicuity in Urban Environment: A Case of London

“…Rambu lalu lintas umumnya dibuat menggunakan material retroreflektif yang mampu memproduksi luminasi atau kuat cahaya yang cukup dan meningkatkan visibilitas pengguna jalan secara signifikan khususnya di malam hari (Kai et al, 2010). Penggunaan material ini juga dinilai mampu memantulkan kembali cahaya yang dihasilkan lampu depan kendaraan ke pengemudi (Carlson et al, 2017;Tyrrell et al, 2016). Namun demikian, pengaplikasian material retroreflektif juga tidak selalu efektif, bergantung dengan kondisi dan lingkungan rambu lalu lintas dioperasikan.…”

“…Kemungkinan untuk menambahkan pencahayaan mandiri pada rambu akan lebih besar apabila latar di belakang rambu semakin rumit dan kompleks. Tingkat kerumitan background akan menyebabkan kebutuhan pencahayaan meningkat dan ukuran rambu yang semakin besar (Carlson et al, 2017). Meskipun telah menggunakan material retroreflektif atau menambah penchayaan untuk rambu, kemungkinan rambu untuk mencolok dan mudah diidentifikasi akan berkurang apabila rambu ditempatkan pada lingkungan dengan latar yang memiliki luminance pencahayaan yang tinggi (Boyce, 2009).…”

“…Dalam kasus conspicuity di lingkungan perkotaan dan jalan raya, kehadiran objek dengan kontras yang tinggi berkaitan dengan kekompleksitasan lingkungan yang tinggi pula (Cavalcante et al, 2014). Salah satu cara yang digunakan untuk menetralkan efek meningkatnya kompleksitas di latar lingkungan pelingkup adalah dengan meningkatkan nilai luminasi cahaya (Carlson et al, 2017;Paulmier et al, 2001). Davoudian juga beranggapan ketika nilai kontras luminasi bertambah, nilai conspicuity juga akan meningkat seiring dengan bertambahnya jarak antara target dan pencahayaan di background pelingkup (Davoudian, 2017).…”