In this twenty-first century and modern society, the number accident and crashes have been biggest concern due to the increase in transportation system and changes in speed limits. Speed limits have been implemented in the US since 1861 and it has resulted in minimizing accidents so far. But, as like all, they need to be updated whenever required and this essay discusses on the reasons why this is the right time to have changes in the speed at which vehicles are allowed to travel on the road, especially on freeways and exits.
As we know, it is the prevailing speed which is generally used as a base to determine the speed limit on a certain road. It is to be accepted that these days, this prevailing speed, the speed at which 85 percent of people travel, is varying a lot when compared with the authorized maximum speed of the same road. This is leading to a situation where very few drivers who want to clearly follow the law are eventually becoming blockers of the traffic and in fact, also leading to a scope for accidents to occur. A study by the Louisiana Transportation Research center indicated that at, only 6 of 39 groups rejected the hypothesis that an increase in speed limit does not lead to an increase in crash rate. Also, the below table (Table 1. taken from US DOT) must be noted which says that crash rates in freeways in Michigan are higher when the speed limit is 55mph as compared to those where the limit is extended to 70mph.
Table 1. Average Crash, Injury, and Fatality Rates on Michigan Freeways, 2004 to 2012
The modern roads are surely a tempting factor for drivers to increase their speed. With the kind of uninterrupted freeways, it is a given that the existing speed limits are considered outdated by most of us. As per AAA’s 2014 traffic survey, 46.1 percent of people say that they exceeded the speed limit by 15mph at the freeways during that past month and 43.5 percent say that they did the same but only till 10 mph. The reason is obvious that they feel the roads are free to move and hence why not use the conditions to save some time. This also evokes the idea of using electronic speed limit boards and thereby change the limits based on traffic conditions. It is also to be noted that in 2015, few states like South Dakota, Montana and Nevada had increased the maximum speed to 85mph and it only helped the drivers and traffic safety.
The one factor which in my feeling is understated is that most of the crashes occurring on freeways are not due to an increased average speed but due to increase in deviation from the average speed. If 10 vehicles are moving on a road, it is not a problem if all the 10 are moving at 65 mph and still not a problem if all of them travel at 75mph. The probability of an accident increases when 8 of them move at 75 mph and the remaining two of them travel at 65mph. This is what is happening these days as most of the drivers tend to increase their speed in free conditions whereas very few like to continue at the specified speed. If we look at fig 1, the crash rate is the lowest when the vehicle is travelling at 85th percentile.
From the study of road section in British Columbia, Canada, it was found that there was significant increase in fatal crashes of about 39.9% over the change in speed increase which were affected over the nearby-segment. Over the course of the study, there were annual averages of 8194 crashes resulting in an insurance claim (2000–2016), 22177 ambulance dispatches for road trauma (2004–2016), 34994 police reported crashes (2000–2015), and 275 fatal crashes (2000–2015). (table 2), In particular it can be said that from the study the number of crashes on affected path are usually twice the increase in speed limit.
Table 2: Annual event count on segments affected by speed limit increases and on segments nearby to speed limit increases, July 2000–June 2016.
All Claims Casualty Claims Police Reported Fatal Crashes Ambulance Dispatches
Total 131,109 25,657 34,994 275 22,177
July 2000–June 2001 4731 1251 1903 20
July 2001–June 2002 6642 1385 2367 22
July 2002–June 2003 6423 1462 2644 14
July 2003–June 2004 6733 1547 2776 14
July 2004–June 2005 7157 1617 2823 23 1856
July 2005–June 2006 7468 1646 2965 29 1943
July 2006–June 2007 8286 1644 2902 14 2039
July 2007–June 2008 8881 1651 2531 27 1981
July 2008–June 2009 8979 1638 2224 22 1812
July 2009–June 2010 8238 1620 1966 22 1859
July 2010–June 2011 8417 1611 1985 14 1857
July 2011–June 2012 8265 1583 1899 10 1700
July 2012–June 2013 8467 1609 1930 19 1619
July 2013–June 2014 9392 1668 1921 16 1654
July 2014–June 2015 10,817 1728 2158 9 1883
July 2015–June 2016 12,213 1997 1974
Average 8194 1604 2333 18 1848
The one factor which keeps on haunting when trying to fasten the speed is the argument that “Speed kills”. It is to be accepted that the increase in speed did lead to an increase in fatalities in many cases and the reason for it is that a fast moving vehicle takes more time to slow down than the slow moving one and it increases the fatality. According to IIHS, 27 percent of all motor vehicle fatalities in 2015 had occurred due to speed related issues. Although, it is to be taken into consideration that a better part of speed related crashes take place in rural roads when compared to that of freeways or interstate highways. The reason behind that is there are many more conflict points, intersections in the rural roads than in freeways. The National Highway Traffic Safety Administration says that the death crashes in rural roads are 2.5 times per mile higher than that in the freeways.
In 2008 W. Warneret conducted study on reasons of exceeding speed limit in Sweden. In his study he found that most of the drivers exceed speed limit just to maintain the flow of traffic and most of the time some use to over speed in urban area were because of hurry and rush to reach destination in limited time. And some users speed because of straight, wide and long stretch of road. In his study he also stated that changing speed limit is one of the difficult task as to have change with respect to controlling and normative behavior of user change. In context with speeding and speeding limit author conclude that ISA (intelligent speed adaptation) and waring system in vehicle might be effective solution for speed variability.
NHTSA conducted survey regarding speeding and speed limit considering driving attitude and speeding behaviors found that usually driver believes to drive over speed limit of plus 5 to 10 mph, majority of them feels speeding on two lane road in city and about 35% of user believe that speed limit is law interstate highways. Drivers believe that speed limit for interstate highway need to be around 67-70 mph or higher and even if speed limit is increased to plus 10 mph, drivers on interstate think they can ride faster than increased speed limit. It was found that there is raise in traffic fatalities if speed limit is increased from 65-70 mph on freeways. A phased approach for several years need to be considered if there is need of increase in speed limit.
In summary, increase in speed limit results in increase in fatalities but most of the time road geometric and its characteristics tend to increase in speed regardless of driver behavior and posted speed. Based on different research paper and literature review, it can be concluded that increasing posted speed limit from 65-70 mph on freeways can result in change of fatalities due to difference in speed.
Additionally, it can be stated that there is no clear idea of increase in speed limit can help in change of crashes in decreasing or increasing. After considering the pros and cons of the increasing speed limits on freeways, my opinion is that we can maintain the safety and still enjoy the opportunity of moving at a faster pace on the well built roads of ours. Safety is always needed to be taken care of, so we need to ensure that the roads have the sufficient infrastructure to encourage higher speeds and then make use of them.
Furthermore, there are no sufficient data on crash and fatalities changes when speed limit and posted speed is changed or increased. Research works can be accompnayed with increased and decreased speed limit to clearly demonstrate effect of better and safe way in road and highway safety in context of traffic fatalities.
- Jayadevan, Athira Swarna. “Effect of Speed Limit Increase on Crash Rate on Rural Two-Lane
- Highways in Louisiana.” LSU Digital Commons, digitalcommons.lsu.edu/gradschool_theses/3785.
- Ary P. Silvano, “Advancing traffic safety an evaluation of speed limits”
- Arup Dutta And David A. Noyce, “Impact of raising speed limits on traffic safety- draft literature review”
- Jeffrey R Brubacher, Herbert Chan, Shannon Erdelyi, Gordon Lovegrove and Farhad Faghihi , “Road Safety Impact of Increased Rural Highway Speed Limits in British Columbia, Canada”