 Q. How much air quality benefit is there from lowering the speed limit by 5 miles per hour?
A. Environmental Protection Agency's MOBILE5 is the federal required motor vehicle emission model used in North Central Texas. After performing a technical analysis on the region's roadway system using MOBILE5, the North Central Texas Council of Governments determined that a combination of reduced speed would benefit the region's air quality without severely compromising the public's safety on area roadways. The table below highlights the various scenarios tested during State Implementation Plan development. Ultimately, the 70 mph to 65 mph and 65 mph to 60 mph combination was the resulting choice.
Q. What roadways are affected by the speed limit reductions?
A. The Speed Limit Reduction Measure website will provide you a geographical map and separate listing of affected roadways. You can reach that site by clicking: http://www.nctcog.org/trans/env_speed_limits/. Specifically, nine counties in North Central Texas are affected. These counties include: Collin, Dallas, Denton, Ellis, Johnson, Kaufman, Parker, Rockwall, and Tarrant Counties.
Q. Why are there speed limit reductions in Johnson, Ellis, Parker, Kaufman, and Rockwall Counties when these counties are not part of the nonattainment area? It seems ridiculous to slow down when you are 50 miles out of town.
A. During State Implementation Plan control strategy development, it was determined that emissions outside the Dallas-Fort Worth nonattainment area are as significant to ozone formation as those within the nonattainment area. In fact, the Texas Commission on Environmental Quality (TCEQ) has shown the "transport" of emissions as far away as Houston contribute to local ozone problems. Therefore, by reducing emissions surrounding the DFW nonattainment area through lower speeds, fewer emissions are transported into the region that can react with existing VOC and NOx emissions.
The following TCEQ website allows the ability to visualize how ozone develops, travels, and dissipates in different areas at different times during the day, dependent on daily weather conditions: http://www.tceq.state.tx.us/cgi-bin/monops/ozone_animation?04. Most recent ozone exceedance days in the Dallas-Fort Worth region occurred on Friday, August 3 and Saturday, August 4, 2001. These animations illustrate how ozone develops.
Q. How will lowering the speed limits help air quality when no one pays attention to the speed limits anyway?
A. The intent of minor speed limit reductions is to lower the overall speed of traveling motorists, recognizing that observed data suggest most motorists travel about 10 percent over posted speed limits. For example, a motorist traveling on a roadway with an original 70 mph speed limit may have been traveling up to 77 mph. By lowering the speed limit to 65 mph, the average speed on that roadway may now be up to 72 mph, resulting in an overall 5 mph reduction. The NCTCOG will be working with the Texas Department of Transportation (TxDOT) to evaluate observed speeds as a result of these speed limit changes.
Q. Do they really expect people to abide by the speed limit reductions? Nobody seems to be slowing down.
A. It is expected that motorists will reduce their speeds by 5 mph since the new speed limits have become legal in 2001. Since the adjustments have recently occurred, it is too early to determine if motorists are "slowing down." Research being performed by TxDOT will indicate if average speeds are less since the speed limit reductions were implemented. In addition, the NCTCOG will be developing an air quality curriculum for local peace officers. One topic to be covered will be the importance of enforcing speed limits. The Regional Transportation Council is in support of enhanced enforcement in order to reduce vehicular emissions and reduce incidents and accidents resulting from erratic speeds. Therefore, anticipate additional enforcement in the future to ensure steady speeds.
Q. Will the speed limit reduction occur only during ozone season (May 1 to October 31)?
A. No. Environmental speed limits are set for year round implementation. This is due to the safety issues to maintain a constant speed limit on these facilities year round.
Q. Why lower the speed limits when the idea is to have better mobility and move traffic out of the way?
A. Environmental speed limits are ineffective in the morning and afternoon peak periods usually experiencing congestion. Since 60 percent of the vehicle miles of travel (VMT) occur in morning and afternoon peak periods, only 40 percent of the VMT is affected. The NCTCOG believes a 5 mph reduction is not significant to effect vehicular mobility in the North Central Texas. However, lower emissions and less incidents and accidents are anticipated as a result of the 5 mph reduction. Other strategies are being implemented in the region to improve mobility and reduce congestion by removing daily VMT through alternate modes of travel. Examples of these strategies include bicycle/pedestrian trails, public transit, carpooling, and employer trip reduction programs.
Q. Wouldn't the money spent on replacing signs, training police officers, etc. be better spent on enforcing the previous speed limits?
A. The amount of money spent on replacing speed limit signs is a one-time implementation cost. Incidentally, this cost was budgeted prior to this effort due to TxDOT's cycle of speed limit sign maintenance and replacement. Training of police officers and the general public is incorporated into existing air quality programs used to explain and educate the region why these efforts are necessary to improve the air we breathe and quality of life.
Q. Why don't we put up signs where it limits SMOKING vehicles instead of SPEEDING vehicles?
A. Targeting smoking vehicles is another program to improve the region's air quality. There are plans in the works to help owners of smoking and high-emitting vehicles get the necessary mechanical repairs needed to correct the emission problems. No one program alone will share the air quality concerns in North Central Texas, as no one item produces the problem.
Q. Why couldn't I vote on the reduction?
A. Throughout the SIP development process, the public had many opportunities to comment on all emission reduction strategies, including the speed limit reduction. The first of these opportunities occurred between August 1999 through October 1999 when NCTCOG had various technical meetings and Steering Committee meetings to develop a control strategy package. The second opportunity was in January 2000 when the TCEQ held public hearings that contained an ample public comment period. The third opportunity to comment was in May 2000 during EPA's public comment period as published in the Federal Register. It is anticipated the next opportunity to provide input on a package of emission reduction control strategies may be in the summer of 2003 when the region works with TCEQ to develop a new SIP. At this time, the schedule for the new SIP has yet to be finalized. Please contact NCTCOG at (817) 695-9240 if you would like to be notified of future SIP meetings.
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