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Evaluation of bilingual traffic signs

Funding Organisation: National Assembly for Wales


The National Assembly for Wales (NAW) commissioned a review of the available research related to bilingual Variable Message Signs (VMS). This review is the first step in this research programme, which is intended to provide advice to those responsible for developing a strategy for the deployment of VMS signs in Wales.

The main aims of the driving simulator experiments were:

  • To determine whether or not the visual distraction associated with bilingual VMS signs of different configurations (length, complexity) impacted on driving performance.
  • To investigate whether drivers operating in a complex environment were able to obtain and comprehend/recall all the information presented on a bilingual VMS sign.

Results showed that:

  • There were no differences in driver performance between the monolinguals and the bilinguals. Both were able to read the two-line (monolingual and bilingual) signs with no compensatory effects in their speed.
  • The four-line bilingual signs did impact on driving performance in that mean speed across the section of the road where the sign was visible was significantly decreased. However the speed changes were typically less than 1.5 mph
  • Contrary to the results reported in the tachistoscope trials (measuring reading time), a separation line placed between the two languages on a four-line bilingual sign, made no difference to driver performance.

The sequencing of signs was also studied, in that different arrangements of signs were tested. The disruption of a sequence by a non-standard sign had no impact on driving performance.

In conclusion, it appeared that four-line bilingual VMS signs comprising two lines of text in each language were read by both monolingual and bilingual drivers in a manner that more closely approximated a two-line monolingual sign. This being the case it is probable that the deployment of four-line bilingual signs on Welsh motorways is unlikely to result in a significant reduction in safety. Furthermore language demarcation and learning will improve performance.