Related Experiment Video
Updated: Apr 19, 2026

Trajectory Data Analyses for Pedestrian Space-time Activity Study
Published on: February 25, 2013
An example of the usefulness of joinpoint trend analysis for assessing changes in traffic safety policies
Gregorio Barrio1, José Pulido2, María J Bravo2
1Escuela Nacional de Sanidad, Instituto de Salud Carlos III, Avenida Monforte de Lemos, 3-5, 28029 Madrid, Spain.
Aim:
To show the usefulness of joinpoint trend analysis for assessing changes in traffic safety policies.
Methods:
Trends in driver death rates from traffic injury stratified by alcohol involvement in Spain during 2001-2011 were characterized with joinpoint regression to observe how changes in these rates match in time with the implementation of traffic regulations and interventions.
Results:
Both alcohol-related (blood alcohol concentration >0.3g/l) and non-alcohol-related rates decreased similarly (10-11% annually) during 2001-2011, although the former showed an earlier (2003 joinpoint) acceleration of the downward trend than the latter (2006 joinpoint); both joinpoints matched in time with relevant road safety interventions.
Conclusions:
These results, which are consistent with results from previous analytical studies, show that joinpoint trend analysis, although not valid for causal inference, is useful for assessing changes in traffic safety policies. This methodology can be easily extended to other risk factors, such as excessive speeding or not wearing a seat belt.
Related Concept Videos
Survey Safety
Hypothesis Test for Test of Independence
H0: The two variables (factors)...
Application of Rates of Change
Introduction to Test of Independence
The test statistic for a test of independence is similar to that of a goodness-of-fit test:
Determination of Expected Frequency
Observational Studies
There are three types of observational studies – Prospective, retrospective, and cross-sectional.
Prospective Study
Prospective studies, also known as longitudinal or cohort studies, are carried out by collecting future data from groups sharing similar characteristics. One...

