I found two tracks will be overlapped when I plot them at the same time. How to seperate them?

My common:

gdPlot(list("A"=track_a,"B"=track_b,genomeAxis),minBase = 0, maxBase =141213000, labelCex = 1)

> sessionInfo() 
R version 3.3.1 (2016-06-21)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows >= 8 x64 (build 9200)

locale:
[1] LC_COLLATE=Chinese (Simplified)_China.936  LC_CTYPE=Chinese (Simplified)_China.936    LC_MONETARY=Chinese (Simplified)_China.936
[4] LC_NUMERIC=C                               LC_TIME=Chinese (Simplified)_China.936    

attached base packages:
[1] grid      stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] GenomeGraphs_1.32.0  biomaRt_2.28.0       BiocInstaller_1.22.3

loaded via a namespace (and not attached):
 [1] Rcpp_0.12.5          IRanges_2.6.1        lattice_0.20-33      XML_3.98-1.4         bitops_1.0-6         DBI_0.4-1            stats4_3.3.1        
 [8] RSQLite_1.0.0        flexmix_2.3-13       S4Vectors_0.10.1     tools_3.3.1          Biobase_2.32.0       RCurl_1.95-4.8       parallel_3.3.1      
[15] BiocGenerics_0.18.0  AnnotationDbi_1.34.3 nnet_7.3-12          modeltools_0.2-21