Lane Departure Countermeasures	Highest Speed Impact (mph)	CMF1	Other Crash Impacts1	Costs2	Usage Within Iowa	Iowa-Specific Guidance
Chevrons/signs/oversized chevrons
chevrons	-1.6	0.75 to 0.96	N/A	$	common	refer to MUTCD
chevrons/warning signs	N/A	0.56	N/A	$	common	refer to MUTCD
oversized chevrons	N/A	N/A	N/A	$	occasional
On-pavement markings
on-pavement curve sign	-7	N/A	N/A	$	limited
Vertical treatments
post mounted delineators	-8	0.70 to 0.80	N/A	$	limited	refer to MUTCD
conspicuity for chevron posts	-2.2	N/A	N/A	$	limited
Dynamic speed feedback signs
DSFS on curves	-7.9	0.93 to 0.95	N/A	$$	limited
Longitudinal rumble strips
centerline rumble strips	N/A	0.67 to 0.91	-25 to -37%	$$$	occasional
shoulder rumble strips	N/A	0.79 to 0.90	-8 to -70%	$$$	common
edgeline rumble stripes	N/A	0.50 to 1.30	N/A	$$$	tested
Roadway treatments
paved shoulder	N/A	0.81	-8%	$$$	widespread	Section 3D-6 Iowa Design manual
Safety Edge	N/A	0.94		$$	occasional	Section 3D-6 Iowa Design manual
high friction treatment	N/A	N/A	-20 to -25%	$$	limited
Lane narrowing
wider edge lines	N/A	0.38	-27%	$	no experience
Lane narrowing