U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
202-366-4000

Skip to content
Facebook iconYouTube iconTwitter iconFlickr iconLinkedInInstagram

Policy and Governmental Affairs
Office of Highway Policy Information

FHWA Home / Policy & Governmental Affairs / Highway Policy Information / Post-event Connected Vehicle Data Exploration - Lessons Learned

Post-event Connected Vehicle Data Exploration - Lessons Learned

Table of Contents

5. Data Insights Explored

5.1: dentification of Vehicle Hard Brake and Acceleration Geolocations

CV data provide insights into vehicle acceleration and deceleration events, pinpointing specific geolocations with timestamps. While a single individual event may not highlight potential infrastructure or operational issues, clusters of such events with high frequency of occurrence in specific roadway areas could signal the potential of infrastructure inadequacies such as, curvature, grade, sight distance, and pavement conditions. In addition, operating challenges, such as congestion and varying speeds among vehicles, may also be potential issues.

5.1.a: OEM CV Data

The OEM post-CV data explored have brake and acceleration event data only for these events exceeding a threshold value associated with longitudinal maneuvers. While the OEM’s specification of a hard brake is not available, AASHTO’s A Policy on Geometric Design of Highways and Streets specifies a maximum of deceleration of 3.4 m/s2 for sight distance computation.

Several approaches were used to analyze the OEM post-CV brake maneuver data. The first one plotted out all individual events on a roadway GIS map. This enables direct observation of such events visually. While this approach offers visual cues on geolocations related to where such events are, it lacks a quantitative measure (e.g., number of events per unit area or unit roadway length) for systematic comparison and ranking. The second approach developed to overcome the issue was through density computation for each predefined zone. In this case, a 2 kilometer (km) by 2 km square (4 km2) zone is defined and used for Florida. The entire state was divided into many thousands of such square zones. Events that occurred in each zone were counted and the density of such events was visually displayed. Obviously, the size of the zone can be structured in any size analyst’s desire. The zone establishment facilitates event frequency computation and identification of high frequency locations. The third approach was computing event density per roadway length. To enable comparison on a common base, a fourth approach can further be developed to divide the third approach result by their corresponding AADT values. In other words, the measure is the result of the number of events per AADT for a unit length of roadway segments. This normalization process has enabled direct comparisons across different roadways.

Figures 2 and 3 illustrate the zonal hard acceleration and hard brake event densities, respectively. The bigger the dot, the higher the number of events that occurred in the 4 km2 zone during the hour. Visual maps like these help analysts expedite the geolocating of high frequency locations. In addition, geolocation density data can be further analyzed by hour of the day together with average speeds. Figure 4 illustrates the hard brake event counts and average speed distribution of the highest frequency area over hours of the day.

Figure 2: Illustrating hard acceleration densities in 4 square km by hour of the day and average speed

This color-coded map of the state Florida illustrates hard acceleration densities and average speed in four square kilometers at seven in the morning. Total hard acceleration counts range from less than ten to more than 299. Average speed generally stays between 20 and 80 kilometers per hour across the region.

Source: FHWA Office of Highway Policy Information.

Figure 3: Hard brake densities per 4 square km by hour of the day and average speed

This color-coded map of the state Florida illustrates hard brake densities and average speed in four square kilometers at nine in the morning. Total hard brake counts range from less than ten to more than 299. Average speed generally stays between 20 and 80 kilometers per hour across the region.

Source: FHWA Office of Highway Policy Information.

Figure 4: Hard brake counts and average speed in the highest frequency area (4 km²) by hour of the day

This cluster bar chart illustrates total hard brake counts and average speed distribution of the highest frequency area by hour of the day. The left y-axis represents total counts from 0 to 300, the right y-axis represents average speed in kilometers per hour from 0 to 120, and the x-axis represents hour of the day. Total counts are highest between 7 in the morning and 5 in the evening. Average speed is generally higher outside this window, peaking above 100 kilometers per hour at 1 in the morning.

Source: FHWA Office of Highway Policy Information.

CV data events can be durational and transitional. For example, seatbelts latched/unlatched, wipers on/off, headlight on/off are durational as they typically sustain a long period of time. Acceleration and brake are transitional as they would sustain for only a short period of time. Acceleration and brake analysis can be integrated with seatbelt, wiper, and headlight status, yielding additional information. Figures 5 and 6 shows hard brake and acceleration counts and maximum speed for each event combination.

Figure 5: Counts of HA and HB events by wiper and seatbelt states

This cluster bar chart illustrates the total counts of hard acceleration (HA) and hard braking (HB) by wiper and seatbelt state. The y-axis represents total counts in millions on a scale from 0.00 to 2.00. The x-axis shows seven categories indicating HA or HB by wiper and/or seatbelt state. The first category is HB/Wiper. In 6.8 percent of HBs, the wiper was activated, and in 93.2 percent of HBs, the wiper was not activated. The second category is HA/Wiper. In 2.1 percent of HAs, the wiper was activated, and in 97.9 percent of HAs, the wiper was not activated. The third category is HB/Seatbelt. In 73.3 percent of HBs, the seatbelt was latched, and in 26.7 percent of HBs, the seatbelt was unlatched. The fourth category is HA/Seatbelt. In 68.3 percent of HAs, the seatbelt was latched, and in 31.7 percent of HAs, the seatbelt was unlatched. The fifth category is HA and Wiper Activated/Seatbelt. In 85.7 percent of HAs with the wiper activated, the seatbelt was latched, and in 14.3 percent of HAs with the wiper activated the seatbelt was unlatched. The sixth category HB and Wiper Activated/Seatbelt. In 86.9 percent of HBs with the wiper activated, the seatbelt was latched, and in 13.1 percent of HBs with the wiper activated, the seatbelt was unlatched. The seventh category is Seatbelt. In 70.4 percent of the total counts the seatbelt was latched, and in 29.6 percent of the total counts, the seatbelt was unlatched.

Source: FHWA Office of Highway Policy Information.

Figure 6: Maximum speed of HA and HB events by wiper and seatbelt states

This cluster bar cart illustrates maximum speed by hard acceleration (HA) and hard braking (HB) and wiper and seatbelt state. The y-axis represents the maximum speed in kilometers per hour from 0 to 350. The x-axis shows seven categories indicating HA or HB by wiper and/or seatbelt state. The first category is HB/Wiper. HBs with wiper activated reach a maximum speed of about 200, and HBs with the wiper not activated, reach a maximum speed of about 250. The second category is HA/Wiper. HAs with the wiper activated reach a maximum speed of about 150, and HAs with the wiper not activated reach a maximum speed of about 340. The third category is HB/Seatbelt. HBs with the seatbelt latched reach a maximum speed of about 240, and HBs with the seatbelt unlatched reach a maximum speed of about 250. The fourth category is HA/Seatbelt. HAs with the seatbelt latched reach a maximum speed of about 230, and HAs with the seatbelt unlatched reach a maximum speed of about 340. The fifth category is HA and Wiper Activated/Seatbelt. HAs with the wiper activated and seatbelt latched reach a maximum speed of about 140, and HAs with the wiper activated and seatbelt unlatched reach a maximum speed of about 130. The sixth category is HB with Wiper Activated/Seatbelt. HBs with the wiper activated and seatbelt latched reach a maximum speed of about 200, and HBs with the wiper activated and seatbelt unlatched reach a maximum speed of about 140. The seventh category is Seatbelt. With the seatbelt latched, maximum speed reaches about 240, and with the seatbelt unlatched, maximum speed reaches about 340.

Source: FHWA Office of Highway Policy Information.

5.1.b: JPO CV Pilot Data

Unlike the OEM CV acceleration or deceleration event data, the JPO Pilot post-CV data contains all acceleration and deceleration maneuvering data covering 3 axes (longitudinal, lateral, and vertical) plus yaw rate. This analysis focuses only on longitudinal and lateral (turning) movements. The lateral acceleration data offer additional information related to vehicle rollover tied with roadway superelevation, curvature, and pavement condition. With the JPO Pilot post-CV data exploration, hard acceleration for longitudinal maneuvers is defined as acceleration equal to or exceeding 3.4 m/s2. Excessive lateral acceleration is defined as 2.4 m/s2 (0.25g).

Figure 7 shows different maneuvers based on longitudinal acceleration states. And Figure 8 shows different maneuvers based on lateral acceleration states.

Figure 7: Longitudinal acceleration points with different maneuver categories

This map shows longitudinal acceleration points with different maneuver categories in Tampa, Florida. Most points represent either soft brakes (greater than negative 3.4 and less than 0 meters per second square) or soft accelerations (greater than or equal to 0 and less than 2.4 meters per second square). The map also shows two instances of hard acceleration (greater than or equal to 2.4 meters per second square).

Source: FHWA Office of Highway Policy Information.

Figure 8: Lateral acceleration points with different maneuver categories

This map shows lateral acceleration points with different maneuver categories on Interstate 80 between Evanston and Rock Springs, Wyoming. Most of the road shows moderate maneuvers (less than 1 meter per second square), but there are also several instances of severe maneuvers (greater than or equal to 1 meter per second square) as the road gets closer to Rock Springs.

Source: FHWA Office of Highway Policy Information.

5.2: Seatbelt Usage Exploration

Seatbelts save lives. While seatbelt usage data lays the foundation for safety work, seatbelt data gathering has always been challenging as the predominant survey method lacks microlevel information. For example, few drivers could tell when they are buckled, unbuckled, or re-buckled during a trip, and percentages of travel time and travel distance that they buckled or unbuckled.

CV event data covers seatbelt usage, enabling the analysis of seatbelt latching status by time of the day, day of the week, and month of the year. In addition, CV data offer information on seatbelt usage status based on vehicle miles traveled (VMT) and vehicle hours traveled (VHT), vehicle speed, and journey progress (e.g., the start of a trip, the end of a trip).

5.2.a: OEM CV Seatbelt Data

Seatbelt status includes latched and unlatched while a vehicle’s engine is on for drivers and front passengers. A simple count of latched and unlatched events can produce a summary of basic parameters, such as percentages of latched and unlatched in terms of the number of such activities. Frequency alone information on seatbelt latched or unlatched status is not sufficient to measure seatbelt usages. For example, a single latch/unlatch action does not necessarily indicate that the seatbelt is used less than multiple latch/unlatch actions. To provide a fuller picture, seatbelt latched/unlatched event data was transformed into seatbelt latched/unlatched state information with associated trips. This transformation enables the analysis of seatbelt usage by VMT, VHT, speed, and vehicle journey progress.

Figures 9 and 10 show the driver and front passenger seatbelt latched/unlatched durations by average travel speed, respectively.

Figure 9: Driver seatbelt usage by average speed thresholds

This cluster bar chart shows average travel time and percent of total above average speed thresholds by driver seatbelt status. The y-axis represents average travel time in minutes from 0 to 60, and the x-axis represents average speed thresholds in kilometers per hour from 20 to 120. At 20 kilometers per hour, 65.5 percent of drivers have a latched seatbelt and 34.5 percent of drivers do not. The latched group has a travel time near 20 minutes, and the unlatched group has a travel time near 10 minutes. At 40 kilometers per hour, 69.4 percent of drivers have a latched seatbelt and 30.6 percent do not. The latched group has a travel time of about 25 minutes, and the unlatched group has a travel time near 10 minutes. At 60 kilometers per hour, 69.8 percent of drivers have a latched seatbelt and 30.2 percent do not. The latched group has a travel time near 35 minutes, and the unlatched group has a travel time near 15 minutes. At 80 kilometers per hour, 67.5 percent of drivers have a latched seatbelt and 32.5 percent do not. The latched group has a travel time near 50 minutes, and the unlatched group has a travel time near 25 minutes. At 90 kilometers per hour, 64.8 percent of drivers have a latched seatbelt and 35.2 percent do not. The latched group has a travel time near 55 minutes, and the unlatched group has a travel time near 30 minutes. At 100 kilometers per hour, 61.0 percent of drivers have a latched seatbelt and 39.0 percent do not. The latched group has a travel time near 60 minutes, and the unlatched group has a travel time near 40 minutes. At 120 kilometers per hour, 44.9 percent of drivers have a latched seatbelt and 55.1 percent do not. The latched group has a travel time near 40 minutes, and the unlatched group has a travel time near 50 minutes.

Source: FHWA Office of Highway Policy Information.

Figure 10: Passenger seatbelt usage by average speed thresholds

This cluster bar chart shows average travel time and percent of total above average speed thresholds by passenger seatbelt status (note: unoccupied passenger journeys are excluded). The y-axis represents average travel time in minutes from 0 to 120, and the x-axis represents average speed thresholds in kilometers per hour from 20 to 120. At 20 kilometers per hour, 79.8 percent of passengers have a latched seatbelt and 20.2 percent do not. The latched group has a travel time near 30 minutes, and the unlatched group has a travel time near 10 minutes. At 40 kilometers per hour, 84.8 percent of passengers have a latched seatbelt and 15.2 percent do not. The latched group has a travel time near 40 minutes, and the unlatched group has a travel time near 10 minutes. At 60 kilometers per hour, 88.9 percent of passengers have a latched seatbelt and 11.1 percent do not. The latched group has a travel time near 60 minutes, and the unlatched group has a travel time near 15 minutes. At 80 kilometers per hour, 92.2 percent of passengers have a latched seatbelt and 7.8 percent do not. The latched group has a travel time near 90 minutes, and the unlatched group has a travel time near 10 minutes. At 90 kilometers per hour, 93.8 percent of passengers have a latched seatbelt and 6.2 percent do not. The latched group has a travel time near 100 minutes, and the unlatched group has a travel time near 10 minutes. At, 100 kilometers per hour, 95.8 percent of passengers have a latched seatbelt and 4.2 percent do not. The latched group has a travel time near 120 minutes, and the unlatched group has a travel time near 5 minutes. At 120 kilometers per hour, 94.2 percent of passengers have a latched seatbelt and 5.8 percent do not. The latched group has a travel time near 110 minutes, and the unlatched group has a travel time near 10 minutes.

Source: FHWA Office of Highway Policy Information.
Note: Unoccupied passenger journeys excluded.

Similarly, Figures 11 and 12 show the driver and front passenger seatbelt durations by average travel distances, respectively.

Figure 11: Driver seatbelt usage by travel distances

This cluster bar chart shows average travel time and percent of total in each travel distance range by driver seatbelt status. The y-axis represents average travel time in minutes from 0 to 600, and the x-axis represents average travel distance ranges in kilometers from 0 to 10 kilometers through more than 1000 kilometers. Traveling 0 to 10 kilometers, 40.7 percent of drivers have a latched seatbelt and 59.3 percent do not. For both groups, the travel time is below 20 minutes. Traveling 10 to 20 kilometers, 52.0 percent of drivers have a latched seatbelt and 48.0 percent do not. For both groups, the travel time is below 30 minutes. Traveling 20 to 30 kilometers, 55.3 percent of drivers have a latched seatbelt and 44.7 percent do not. For both groups, the travel time is below 50 minutes. Traveling 30 to 40 kilometers, 56.8 percent of drivers have a latched seatbelt and 43.2 percent do not. For both groups, the travel time is below 100 minutes. Traveling 40 to 50 kilometers, 58.3 percent of drivers have a latched seatbelt and 41.7 percent do not. For both groups, the travel time is below 100 minutes. Traveling 50 to 100 kilometers, 60.8 percent of drivers have a latched seatbelt and 39.2 percent do not. For both groups, the travel time is below 100 minutes. Traveling 100 to 150 kilometers, 63.1 percent of drivers have a latched seatbelt and 36.9 percent do not. For both groups, the travel time is below 100 minutes. Traveling 150 to 200 kilometers, 64.6 percent of drivers have a latched seatbelt and 35.4 percent do not. For the latched group, travel time is about 100 minutes, and for the unlatched group, travel time is less than 100 minutes. Traveling 200 to 300 kilometers, 62.1 percent of drivers have a latched seatbelt and 37.9 percent do not. For the latched group, travel time is above 100 minutes, and for the unlatched group, travel time is below 100 minutes. Traveling 300 to 500 kilometers, 55.8 percent of drivers have a latched seatbelt and 44.2 percent do not. For both groups, the travel time is above 100 minutes. Traveling 500 to 1000 kilometers, 53.0 percent of drivers have a latched seatbelt and 47.0 percent do not. For the latched group, travel time is near 200 minutes, and for the unlatched group, travel time is more than 100 minutes. Traveling more than 1000 kilometers, 67.3 percent of drivers have a latched seatbelt and 32.7 percent do not. For the latched group, travel time is about 500 minutes, and for the unlatched group, travel time is more than 300 minutes.

Source: FHWA Office of Highway Policy Information.

Figure 12: Passenger seatbelt usage by travel distances

This cluster bar chart shows average travel time and percent of total in each travel distance range by passenger seatbelt status (note: unoccupied passenger journeys are excluded). The y-axis represents average travel time in minutes from 0 to 400, and the x-axis represents average travel distance ranges in kilometers from 0 to 10 kilometers through more than 1000 kilometers. Traveling 0 to 10 kilometers, 78.7 percent of passengers have a latched seatbelt and 21.3 percent do not. For both groups, travel time is less than 50 minutes. Traveling 10 to 20 kilometers, 75.8 percent of passengers have a latched seatbelt and 24.2 percent do not. For both groups, travel time is less than 50 minutes. Traveling 20 to 30 kilometers, 73.6 percent of passengers have a latched seatbelt and 26.4 percent do not. For both groups, travel time is less than 50 minutes. Traveling 30 to 40 kilometers, 72.5 percent of passengers have a latched seatbelt and 27.5 percent do not. For both groups, travel time is less than 50 minutes. Traveling 40 to 50 kilometers, 73.3 percent of passengers have a latched seatbelt and 26.7 percent do not. For the latched group, travel time is about 50 minutes, and for the unlatched group, travel time is less than 50 minutes. Traveling 50 to 100 kilometers, 73.2 percent of passengers have a latched seatbelt and 26.8 percent do not. For the latched group, travel time is about 50 minutes, and for the unlatched group, travel time is less than 50 minutes. Traveling 100 to 150 kilometers, 77.7 percent of passengers have a latched seatbelt and 22.3 percent do not. For the latched group, travel time is more than 50 minutes, and for the unlatched group, travel time is less than 50 minutes. Traveling 150 to 200 kilometers, 83.7 percent of passengers have a latched seatbelt and 16.3 percent do not. For the latched group, travel time is about 100 minutes, and for the unlatched group, travel time is less than 50 minutes. Traveling 200 to 300 kilometers, 87.7 percent of passengers have a latched seatbelt and 12.3 percent do not. For the latched group, travel time is about 150 minutes, and for the unlatched group, travel time is less than 50 minutes. Traveling 300 to 500 kilometers, 89.3 percent of passengers have a latched seatbelt and 10.7 percent do not. For the latched group, travel time is about 200 minutes, and for the unlatched group, travel time is less than 50 minutes. Traveling 500 to 1000 kilometers, 96.0 percent of passengers have a latched seatbelt and 4.0 percent do not. For the latched group, travel time is about 350 minutes, and for the unlatched group, travel time is less than 50 minutes. No data are shown for traveling more than 1000 kilometers.

Note: Unoccupied passenger journeys excluded.
Source: FHWA Office of Highway Policy Information.

Tables 1 and 2 show the percentages of seatbelt usages by average travel speed thresholds and travel distances, respectively.

Table 1: Seatbelt usages in percentage by average travel speed thresholds
Seatbelt Average Travel Speed Thresholds (KM/H)
20 40 60 80 90 100 120
Driver 65.5 69.4 69.8 67.5 64.8 61 44.9
Passenger 79.8 84.8 88.9 92.2 93.8 95.8 94.2
Table 2: Seatbelt usages in percentage by travel distances
Seatbelt Travel Distances (KM)
0-10 10-20 20-30 30-40 40-50 50-100 100-150 150-200 200-300 300-500 500-1000 >1000
Driver 40.7 52 55.3 56.8 58.3 60.8 63.1 64.6 62.1 55.8 53 67.3
Passenger 78.7 75.8 73.6 72.5 73.3 73.2 77.7 83.7 87.7 89.3 96 NA

5.2.b: JPO CV Pilot Data

Seatbelt data associated with the JPO Pilot CV data is not available.

5.3: Trip Distribution by Length

5.3.a: OEM CV Data

Trip distribution by trip length information is critically needed for travel demand modeling associated with transportation planning. The post-CV data analysis of the OEM CV data offers such information as illustrated in Figures 13-15. Due to privacy considerations, OEM CV data do not provide trip information, which is defined by the starting and ending points of travel. Instead, it provides only journey information, which is defined by the points where a car's engine starts and stops. Figure 13 shows the total number of journeys by travel distance. From the distribution, we can understand that journeys of less than 10 KM are predominant. Figure 14 shows the average speed, maximum speed, and average travel time for different travel distances. Figure 15 shows the journey frequency at which the front passenger seat is occupied.

Figure 13: Number of journeys by travel distances

This bar chart shows the number of journeys over journey distance range. The y-axis represents total journeys in millions from 0.0 to 1.8, and the x-axis represents journey distance ranges in kilometers from 0 to 10 kilometers through more than 1000 kilometers. This chart shows about 1.7 million journeys between 0 and 10 kilometers, about 0.4 million journeys between 10 and 20 kilometers, about 0.2 million journeys between 20 and 30 kilometers, about 0.2 million journeys between 30 and 40 kilometers, about 0.1 million journeys between 40 and 50 kilometers, about 0.2 million journeys between 50 and 100 kilometers, about 0.1 million journeys between 100 and 150 kilometers, about 0.1 million journeys between 150 and 200 kilometers, less than 0.1 million journeys between 200 and 300 kilometers, and less than 0.1 million journeys between 300 and 500 kilometers. No data are shown for 500 to 1000 kilometers or more than 1000 kilometers.

Source: FHWA Office of Highway Policy Information.

Figure 14: Travel speed and travel time by travel distances

This cluster bar chart shows speed and travel time distribution over journey distance range. The left y-axis represents speed in kilometers per hour from 0 to 300, the right y-axis represents average travel time in minutes from 0 to 800, and the x-axis represents journey distance ranges in kilometers from 0 to 10 kilometers through more than 1000 kilometers. For each range on the x-axis, three bars representing average speed, max speed, and average travel time are shown. For most categories, average travel time is the smallest bar, max speed is the largest bar, and average speed is somewhere in the middle. This pattern changes in the last two categories. For journeys between 500 and 1000 kilometers, the average speed is about 100 kilometers per hour, the max speed is about 200 kilometers per hour, and the average travel time is about 400 minutes. For journeys more than 1000 kilometers, average speed is about 100 kilometers per hour, max speed is about 175 kilometers per hour, and average travel time is near 800 minutes.

Source: FHWA Office of Highway Policy Information.

Figure 15: Frequencies of journeys occupied with front passenger by travel distances.

This cluster bar chart shows journeys in each travel distance range. The y-axis represents number of journeys in millions from 0.0 to 1.6, and the x-axis represents average travel distance ranges in kilometers from 0 to 10 kilometers through more than 1000 kilometers. Between 0 and 10 kilometers, there are about 1.4 million total journeys and less than 0.2 million journeys with passengers. Between 10 and 20 kilometers, there are about 0.4 million total journeys and less than 0.2 million journeys with passengers. Between 20 and 30 kilometers, there are about 0.2 million total journeys and less than 0.2 million journeys with passengers. Between 30 and 40 kilometers, there are less than 0.2 million total journeys. Between 40 and 50 kilometers, there are less than 0.2 million total journeys. Between 50 and 100 kilometers, there are less than 0.2 million total journeys. Between 100 and 150 kilometers, there are less than 0.2 million total journeys. Between 150 and 200 kilometers, there are less than 0.2 million total journeys. Between 200 and 300 kilometers, there are less than 0.2 million total journeys. Between 300 and 500 kilometers, there are less than 0.2 million total journeys. No data are shown for journeys between 500 and 1000 kilometers or more than 1000 kilometers.

Source: FHWA Office of Highway Policy Information.

5.4: Posted Speed Limits vs. the 85th Actual Travel Speed

5.4.a: JPO Pilot Post-CV Pilot Data

JPO Pilot post-CV TIM data file has roadside speed limit sign information, which is broadcasted to the connected vehicles. The BSM contains actual vehicle travel speed. By conflating the speed limit sign data and the actual vehicle speed information with roadway segments, the exploration further analyzed the similarities between the posted speed limits and the 85th percentile actual speeds. Figure 16 illustrates the results of the analysis along a segment of Interstate 80. Figure 17 illustrates the 85th percentile speed and the posted speed by hour of the day for a sample roadway segment.

Figure 16: Speed differences between the speed limits in TIM and the 85th percentile of actual speeds

This map is color coded to illustrate speed differences between the speed limits in traveler information messages and the 85th percentile of actual speeds on a stretch of road in Wyoming. Generally, the speed difference ranges fall between negative 47.8 to negative 23.8 percent and negative 23.7 percent to negative 6 percent. Where the posted speed limit is 80 miles per hour, the speed difference range reaches negative 100 to negative 47.9 percent. Where the posted speed limit is between 65 and 75 miles per hour, the speed difference range is between negative 5.9 percent and 112.7 percent.

Source: FHWA Office of Highway Policy Information.

Figure 17: Actual 85th percentile traffic speed vs posted speed by hour of the day.

This bar chart illustrates 85th percentile traffic speed versus posted speed (75 miles per hour). The y-axis represents 85th traffic speed in miles per hour from 69 to 80, and the x-axis represents hour of the day. At 1 in the morning, 85th traffic speed is just under 71 miles per hour and the speed difference is negative 6.71 percent. At 6 and 7 in the morning, the 85th traffic speed is just under 75 miles per hour and the speed difference is 0 percent. At 9 in the morning, the 85th traffic speed is 70 miles per hour and the speed difference is negative 6.71 percent. At 2 in the afternoon, the 85th traffic speed is above 73 miles per hour and the speed difference is negative 3.36 percent. At 3 in the afternoon, the 85th traffic speed is nearly 78 miles per hour and the speed difference is 3.36 percent. At 4 in the afternoon, the 85th traffic speed is nearly 76 miles per hour and the speed difference is 0 percent. At 5 in the evening, the 85th traffic speed is near 78 miles per hour and the speed difference is 3.36 percent. At 7 and 8 in the evening, the 85th traffic speed is near 80 miles per hour and the speed difference is 6.71 percent. At 9 in the evening, the 85th traffic speed is just over 78 miles per hour and the speed difference is 6.71 percent. At 10 in the evening, the 85th traffic speed is just over 75 miles per hour and the speed difference is 0 percent. At 11 in the evening, the 85th traffic speed is near 80 miles per hour and the speed difference is 6.71 percent.

Source: FHWA Office of Highway Policy Information.

5.5: Roadway Curvature and Frequency of Vehicle Maneuvers

The BSM data is used to count the frequencies of vehicle maneuvers characterized by acceleration and deceleration changes. These maneuver changes are integrated into the roadway geospatial alignment data. The roadway curvature analyses focused only on JPO’s Pilot WYDOT data that has coverage of many different curvature roadway segments. The hypothesis that the sharper a roadway curve is, the more maneuvers a driver may perform is not observed, though. The limited data set, for example, shows that the sharper a roadway curve is, the steadier the driver (fewer maneuvers) maintains its vehicle operation.

 

Previous | Next

Page last modified on May 9, 2024
Privacy Policy | Freedom of Information Act (FOIA) | Accessibility | Web Policies & Notices | No Fear Act | Report Waste, Fraud and Abuse
U.S. DOT Home | USA.gov | WhiteHouse.gov

Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000